[forum] Warning before necroposting?

Could we possibly add a warning when someone is posting to a thread that is more than X months old? I can't count how often I see someone dreg up a post from 2010 for a comment that adds absolutely nothing or even asks a question that's barely even on the same topic - when they have clearly just stumbled to that post by a search and haven't noticed how old it is.

Something like, "Warning: the post you're commenting on was last posted to 3 years ago. Is this really a continuation of this...

[forum] Warning before necroposting?