I'm certain some of these players could and would cry harassment to a GM if you track them down after game and start offering
unsolicited advice.
If somebody is holding back the group to a noticeable extent they should be embarrassed, maybe they would respect others time at that point. They should be embarrassed about their own performance without anybody having to say anything.
Also, for that matter, who even actually cares if they get embarrassed? I can tell you right now, I wouldn't be nice
at all to these players if SE didn't police the game like they do. I can definitely say you would hate to see my chat off site, or game about these kind of subjects.

Either way, personally, I don't actually offer advice in the first place, so you don't have to worry about me. I threw out my mentor crown a long time ago, though I never offered advice when I had it either.