In general I think the grammar pedants just make themselves look silly and, where the writer is obviously distressed, it just comes across as plain nasty.
Obviously you notice, "should of" instead of "should have" sets my teeth on edge but I would never, ever point it out on a thread.
I must say though, if I open a thread and find the OP is a solid block of text with no paragraph breaks then I usually close it PDQ. Comment? No of course not. Read it? Nope.