Can we please take a step back and remember (rant incoming):
1) Writing is a hobby. We are doing this for fun.
2) Writers are not omniscient. We do not see everything everyone posted ever.
My god. Y'all are way too comfortable going into people's asks and treating it like there isn't an actual person behind the screen. You know how many times I've gone "oh, fuck, I didn't see so-and-so posted that"? So fucking many.
Maybe follow the poster's lead, and if they're not worried about it, you shouldn't be either - or, better idea, don't be a dick about a hobby, period. Going into someone's asks - on anon, no less - to rag on them about "copying" something that the original poster doesn't even see as "copying" is fucking insane. First, if you're going to be an asshole because you feel that strongly about something, come off anon and say it with your chest. Second, I'm sure if you're a reasonable person, there's a way to voice just about every concern without turning it into a witch hunt. If you're that worried, message the original poster, say "hey, I wanted you to see this", and let people talk it out like the mature people we all should be if we're posting the things we're posting. Y'all don't have to come out swinging defending people that probably don't need defending in the first place.
Y'all are going to be the reason people start turning anon off, using the workaround to see who anons actually are, or just not fucking posting anymore.