A streamer I follow who's pretty private about their personal info posted something on twitter that I realized could possibly be used to partially doxx them. Not enough to find their name or anything, but they don't even talk about what country they live in and this was a lot more specific than that. So I did a quick search to see if it actually does turn up info, then DM on discord (I was already a member of their server) and said "Just wanted to let you know that if <personal info is true> then your tweet partially doxxes you."
Naturally this weirded them out and made them really uncomfortable. They said they'd been posting similar info for 2 years and no one else had actually gone and searched it up. Now they have to deal with knowing that someone has that info and just hope I don't have bad intentions (I don't, of course, but why should they believe me?)
What the fuck made me think this was a good idea, or that I was helping? I definitely need to do some self-reflection.
EDIT: Between this and talking to someone irl I may be less dumb than I thought.
You're not friends with this person IRL, you're doing them a favor by letting them know they're fucked up. Don't feel bad that this stranger is weirded about you, thats the parasocial conditioning talking. You're not this person's friend and do not mean anything to them, of course they're weirded out.
Don't feel bad about warning them though.