Based on both decent and not so decent replies, I have made some changes to my original post below.
It would seem a whole new kind of AO3 reader/writer is emerging and it is becoming clear not everyone quite understands how the website community works. Here is some basic guidance on how most people expect you to go about using AO3 to keep this a fun community archive that funtions correctly:
As well as likes, kudos is for when the story was interesting enough to make you finish reading. If it sucked or was badly written, you probably left. If you finished it, you liked it - so kudos.
If you really liked it, you should try to comment. It can be long and detailed or a literal keysmash. Writers don't care, we just love comments.
No critisism unless the author has specifically asked or agreed to hear it (so use your notes to say if you want some constructive feedback). Even constructive critisism is a no-no unless an author note tells you it's okay. No, posting it online is not an open invitation for that. Many people write as a fun hobby or a way to cope with, among other things, insecurity and just want to share. Don't ruin that for them. I've seen so many authors just stop writing coz they can't handle the negative emotions the critism brings, and it's only meant to be a fun thing shared for free (pointing out tagging errors is not included in this).
Do not comment to ask the author to write/update something else. It's tacky and off-putting and will probably have the opposite effect than the one you want.
There is no algorithm, it's an archive. Use the search and filter function to add/remove the pairings/characters/tropes etc. you want to read about and it will find you the fics that fit the bill.
For this to work, writers must tag and rate stories. This avoids readers finding the wrong things and missing the stuff they want. I don't care how cringy that trope is in your eyes - it gets tagged.
The tag exception is if you don't want to tag a million things or spoil your story, you can rate it as "chose not to use warnings," and maybe tag the bare minimum.
Don't censor tags. How can someone exclude a tag if the word isn't typed out correctly? There are no content bans for terms so don't censor them.
If the tags are mostly content/trigger warnings, especially if they are things considered very fucked up or graphic, you might want to use "dead dove - do not eat" to ensure people know that you're not messing around with tags and what they get is exactly what you've warned them about.
Character A/Character B means a ROMANTIC or SEXUAL relationship of some kind. Character A&Character B is PLATONIC, like friendship or family.
Nothing is banned. This is an rule because banning one thing is a slipperly slope to banning another and another, until nothing is allowed anymore. Do not expect anyone to censor for you. Because of the tags system, you are responsible for your own reading experience.
People can create new chapters and sequels/fic series any time after they "complete" a story. So it's considered perfectly normal to subscribe, even to a finished story. You can even subscribe to the author instead just to cover your bases.
Do not repost stories or change the publishing date without an extremely good reason (like a complete top to bottom rewrite or an exchange youve written for going public). It's an archive, not social media. No one cares what's the most recent, only what fits their tag needs.
Instead of deleting a story you wrote if you hate it - consider making it anonymous or orphaning it so others can still enjoy it, without it being connected to your name anymore. If you still want to delete it, fair enough.
It's come to my attention that metaworks ARE allowed on AO3, which is something I wasn't aware of. So if you do post an essay or theory, please tag it as such so others can choose to search for it or exclude it. Art is also allowed.
The only reason this archive works is because NON ONE PROFITS. Do not link to your ko-fi or patreon or mention monetary gain in any way or you violate the terms and risk having your account removed. If anyone does link, it leaves the archive open to people claiming it's for profit and having the whole thing removed.
I KNOW there's plenty more I missed but I'm trying to cover most of the basics that people seem to be struggling with.
I invite anyone to add to this, but please explain, don't berate.
