Em dash, "This isn't X. It's Y.", the rule of 3. These are perfectly good devices — when style and structure fit content. But when spammed by AI, they're not good writing. They're slop.
Of course, much has been said about AI writing tics already. Comments along the lines of "you'll pry the em dash from my cold dead hands" have my sympathy. Much less sympathy for people who use AI to write, even if it's English as a second language, I'd rather hear your unedited draft. Regardless of content, AI tone regresses to wearingly punchy yet bland, like LinkedIn. And in general AI writing smells of the offputting feeling that the writer has not put time and effort thinking into through their work. But again AI writing has been discussed a lot already.
A less mentioned AI tic I see a lot now is a grid of rounded rects. Like AI's writing patterns, there's nothing inherently wrong with rounded rects, in fact they're very nice. But like AI writing, rounded rects are part of a website's AI smell. Not saying any em dash is definitely AI writing or any rounded rect is definitely AI website; they're one factor to take into account.
Often these rounded rects will feel like they should be links, but are not. They will have a short sentence or two claiming some functionality, and on cursor hover will do something eg move up slightly. But clicking them doesn't go anywhere. I think they aren't working links because it's very easy for AI to generate a splashy landing page, but harder to generate a non garbage project, and many AI users are happy with that. Also, AI often lays out text in bullet points or a very structured list of paragraphs, and rounded rects in a grid are the website equivalent of a list of short points.
Rounded rects are actually great (albeit less brilliantly executed in Tahoe), so don't take this as me hating them — I like rounded rects! Unfortunately today they seem common in AI generated sites, for instance hackernews ".dev" posts . And you might object that this is just the base rate, that is, rounded rects are common in both AI and non AI websites, but eh, maybe it's just something about how they're used, but I feel like I can pretty reliably recognize AI rounded rects.