Yeah, I remember getting some wild ones when I was hiring manager
So many women feel the need to mention their young children in their cover letters and CVs. Some young people slip in that they can't drive, a sort of pre-emptive "but it's okay I have a bus pass". So many people go and shove their mental health issues with anxiety and depression in there.
I remember one girl had clearly been told that she needed to explain any gaps in employment in the cover letter (terrible blanket advice), and so had described how she had developed depression after a traumatic miscarriage and spent a year in a terrible spiral getting worse and worse before getting on a new medication that, and I quote, "seemed to be finally starting to work." There are ways she could have written that information if she was desperately wanting to include it (I cannot stress enough that she should not have included a word of it), but the way it was written was almost literally a description of how she would be a horrendously unreliable employee who could dip out at a moment's notice and would never be seen again, while also demonstrating that she cannot determine appropriate professional communication.
(And for the record, the latter is the actual issue. I have no problems at all hiring employees with mental health issues, and did several times hire people in recovery to help them get back on their feet. Only once did that not work out; all others were amazing, and two became some of our best employees - one is now a manager there, in fact. But if an employee can't be trusted not to over share personal information with customers or colleagues, particularly triggering topics... That's a different issue. She did herself no favours at all there, and nor did whoever told her employers will always need employment gaps explaining in a cover letter).
Another guy once wrote in his cover letter "I want this job because after years of messing about I now have a little girl, so I need to sort my life out for her, and if I can't do it even for her then more fool me." Which, like, I admire the drive and passion. But again. Why are you telling an employer that you're a flight risk. Why are you telling us this.
One 18 year old volunteered, unforced, that he was gay. Just right in the cover letter. That he sent to a future employer.
And then, of course, the thousands that send in CVs and cover letters that are horrendously mis-spelled. Again, as an employer, I care dick-all if you're dyslexic or what have you; but I do care that you didn't think it was important to get someone to proofread a professional document for you before submission. That tells me quite a big thing about the level of professionalism I can expect from you in the role. It wasn't massively relevant for the job I was hiring for (escape room game master), but if we'd had slightly different job duties (e.g. writing official soc med posts), that would be the difference between getting an interview or not.
Honestly, half of my role as a hiring manager was just... having to explain to the other hiring manager that she was being biased based on information neither of us should have had in the first place. And she wasn't a bad person, but bias gets you even if you don't want it to. Give yourself the best chance. Don't fuck it by sending in a dumbass cover letter.
