Interesting question. I tend to read the content of the posts, and only occasionally glance to the side to see who wrote the post--usually if there's something remarkable about it (either bad or good). So, I probably don't pick up on stylistic patterns for most individual posters.
All that being said, I feel like I do see a lot of people who (gently or not) challenge the OP about the details they provide--I've not noticed people refraining from saying anything just because the OP is a long-time poster. Of course, sometimes with a long-time poster, people with better memories than I already KNOW extra details--I sometimes see replies like, "Oh no, MIL acting up again? What with her history of boundary-smashing, I think you seriously need to just stay away from her for a while." And the OP hasn't even mentioned much history with MIL, but posters remember it from previous posts (which the OP hasn't even alluded to). I consider that part of the perks of being a tight-knit community, though I think it's perfectly reasonable for someone else to say, "Sorry, I don't remember the history here. Can someone provide links to previous threads?" if they're interested.
I've also seen people say in a thread, "You know, Wynn5000, I've seen several threads from you lately, and you always seem to put in these extra negative details that are unnecessary for the story." I don't know if that's polite or not, but it does happen. Would it be better to send Wynn5000 a PM, if you take a helpful, "you're new here so maybe you didn't know..." tone? Or should you just use the "mental ignore button" and stop reading posts by Wynn5000?