On further thought, I think "geeksplaining" may be an excellent word for this cluster of behaviours, and I may even start using it.

Edit: e.g. my blog got Redditdotted yesterday. Geeksplaining advice "switch to nginx!" No, that doesn't actually work with the stuff I've already said I'm using, you just said it because it's trendy so it occurred to you to say it. Applicable when people say something that's helpy rather than helpful. I foresee this being a vastly useful term.