Checkmarks as bullets on progress/comparison lists I really like, assuming you mean //. The emoji properly put me off looking deeper into whatever it is that I am looking at unless I was really interested to start with.

Both predate common use of LLMs, unless my memory is even more shaky than usual on this, but must have been over-represented in the training data (or something in the tokenising/training/other processes magnifies the effective presence of punctuation) because LLMs seem to love spewing them out.