Posting, fairly rarely since I don't tend to think of something that I believe merits taking up space in someone's feed. Typically, it's going to be a music based post just because music communities tend to be more viable for posting stuff that one person likes without it bothering anyone that doesn't.

Commenting though? By default, anyone posting is okay with receiving comments. And, since I can pick only stuff that is either open for joking, or where the poster is wanting input of some kind, it's essentially a guarantee that any on topic response is okay.

In other words, it's easier to stay relevant in comments than posts, and I prefer to stay topical most of the time