My two cents.
I participate here with the understanding that this is a learning place, both for Spanish and English. Heck, there have been a number of Portuguese and French questions answered, as well, and I seem to recall seeing something in Danish or some such..?
We regularly get treated to spelling and grammar atrocities that are posted by people who presumably are native speakers of the language in which they're writing, eg: "how you say hello in spinol? reply immediately!!".
So in my view, corrections should be a regular part of the activities that all members perform. I believe that if anyone catches a spelling or grammar mistake, he or she should point it out, regardless of what his or her native language is.
I think there are polite ways of doing that, so no feelings ought to be hurt. Sometimes that could even lead to more learning opportunities. Point in case, some of the comments that have been made when someone writes the past tense of "to spell" as "spelt." Pointing it out as an error is an opportunity for some of us to learn that "spelt" is in fact a correct, if not the preferred, spelling of that form of the verb.
I don't mind being wrong and being corrected. I delight in finding new words, and even discovering that I had been living for years with the wrong definition for a word in my mind. I see learning as an ongoing process with no end in sight!
Rudeness and idiocy, now, those are things that definitely should be avoided. But the first one isn't what this thread is about, and the second - it seems like it cannot be avoided, to judge from some of the posts that appear on a daily basis. (Mostly from ephemeral contributors, thank goodness!)