So, in the last couple months, I've gotten a few different people commenting on my fanfiction commenting/reviewing methods. I've been involved in fanfic communities since 2008 and I've reviewed literally thousands of stories. I also like leaving long, fairly detailed comments, and I've had multiple people asking me for tips on commenting and what my process is. I needed to take a little break amidst the chaos of packing for a 2000 mile move, so I thought I'd write up a little guide for tips and tricks on leaving great reviews. So here you go: SG's Guide to Commenting on Fanfics!
First of all, my method. I take notes as I read personally. My preferred method is saving stories to my laptop and then highlighting parts I want to comment on, but there are any number of alternate methods, such as using a note app on your phone or jotting down physical notes in a notebook, if you're old-school like that :)
Then, here are my tips on ways to write great comments! (And a reminder, these are just tips, not rules! There is no Fanfiction Comments Bible I am using here, just my own experience for how I write my comments/reviews, so take or leave any portions of it that you want. But hopefully, if you are new to commenting or wanting to leave more detailed comments, you'll find something helpful here.
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1. First, you can never go wrong with an enthusiastic "OMG I loved this! *keyboard smash* *kudos*" I can guarantee you that there is no author out there who doesn't appreciate unbridled enthusiasm about the content they spent hours, days, weeks, or even months working on.
2. Quote passages that stood out to you, then tell the author how that passage made you feel. From my experience, authors love knowing specific passages that impacted their reader. I usually will format it something like this: *Quote from story* Oh my gosh, this piece of dialogue made me laugh so hard...or... *Quote from story* I seriously teared up here, so beautiful.
3. Were there places where the characterization was just spot on? Let the author know. It can be something simple like "When x character did x, that felt SO in character!"
4. Did the characters make you feel emotions? Again, let the author know. "When x character did x, I wanted to punch them so hard!" or "Aw, when x character kissed x character, I felt so warm and fuzzy!"
5. Was there a descriptive passage that felt super realistic? You can say something like "When you described that waterfall, I felt like I was right there" or "When x character was pulling out that splinter, I was squirming the whole time".
6. For a little bit of a more expert reviewer tip, comment on things that author has done to expand or add to the world. This can look like a variety of different comments, but here are some examples. "I love how you've delved into x character's backstory or psychology with your story. I've always found them intriguing and wondered why they made x choice." "Your OC fits so well into this world. I could totally see this character going about their life during the canon events." "I really enjoy that you're exploring x culture in your story; I loved the description of the festival at the beginning."
7. For a really expert tip, comment on the little easter eggs you notice in fics. From my experience, authors are utterly delighted when readers pick up the little tidbits they've meticulously hidden or ways they've shown off their technical skills. This requires more in-depth knowledge of how writing and stories work however. This can look like comments like these: "OMG, I saw what you did there with that foreshadowing when x character said x!" or "That was really clever how you showed a parallel between this character over here and that character over there."
8. Finally, thank the author! They put lots of effort into creating this piece of art that you've just enjoyed; let them know you appreciate their time, creativity, and effort. And if it's a multi-chapter story or a series, let them know you're invested without being pushy for an update. I like saying something like this at the end of my reviews: "Thank you so much for sharing your work with us! I am so excited to see where the story is going whenever you share the next chapter. Cheers!"
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And of course, remember that a simple comment is better than no comment! I know I'm very much not the only person to have said this, but comments are an essential part of the Fandom ecosystem. If you only have time or energy to leave a quick "I loved it!" then do that! You will make the author's day, I guarantee. But if you're considering whether or not to leave a comment at all, please remember that all fanfic authors are people who have poured enormous amounts of time and effort into the thing you've just enjoyed (to give you an idea, it takes me an average of about 60-80 hours PER CHAPTER to write Gorthauro Estel).
I've also seen posts from people about fears of saying the wrong thing in a review. There are very few "wrong" things to say, but just to allay any fears one might have, I've compiled a quick list of what to avoid in your review.
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Don't beg for updates. Getting an "Update please!" review on a WIP that you haven't been able to work on for whatever reasons is always discouraging. I can understand how a beginning reviewer could see it as a complement, but as someone myself who is slow to update, I can tell you that it only puts a larger sense of pressure, weight, and discouragement on the writer. If you want to let the writer know you are looking forward to an update and are invested in the story, look at my last point in the comment tips above.
Going along with that, don't comment on how long it's been since the story has been updated. During some of my gaps where I just couldn't write for a number of different reasons, I would get frequent comments along the lines of "wow, this story hasn't been updated in a year, are you ever going to update?" Those reviews would make me feel SO bad. I was always intimately aware of how long it had been, and I think most authors are the same. Instead, writing a sweet, enthusiastic review with some of the tips above might just give the author the emotional and mental juice to work on that stalled WIP again.
If the author has a different headcanon about a character, event, etc that doesn't line up with your headcanon, don't comment on it. I recently got a review complaining that I write my Sauron as someone attracted to women. I personally headcanon Sauron as heteroromantic demisexual (which is also what I am), and that's the way I portray him in my fics. If the author's headcanon doesn't line up with yours and it bothers you enough to want to comment on it, that story might just not be for you. If you choose to read the fic, you are choosing to enter into the world of the author's headcanon and you should be respectful of it.
Similarly, if the author makes a choice for where to take their story that you don't care for, don't comment on it. You are perfectly within your rights to stop reading if you don't like the way the author chooses to take their story, but it is their story.
Don't point out mistakes unless you know whether the author is comfortable with it or not. I am personally fine with people pointing out typos or the like to me in public reviews, but some people can be sensitive about it. Check with the author privately rather than leaving a public comment to see what they are comfortable with.
Basically, it comes down to the old adage, if you don't have anything nice to say, don't say anything at all. If you keep your comments positive rather than negative, you're unlikely to say anything "wrong".
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Hopefully, this has been helpful! Now go forth and comment!