Would it be mean of me to say that I also noticed, and that if this were YCM I might in fact be pointing it out (though obviously with a certain degree less satire)?
(Of course, I'd only give serious attention to it if it were in a card -- I'm a compulsory OCG fixer. Bad OCG makes me shiver.)
Not really, the fact that you're refering to something that usually requires one to utilize proper grammar justifies why you would point out such things, but still the fact that no one really pokes you in the eye about grammar HERE just for the sake of correcting a person is what makes the above situation look odd.
Fact of the matter is, on most forums I go to, grammar is pretty much swept under the rug and no one is really called out on messing up something unless it has something to do either writing fiction or if what they're typing can't be read normally due to horrible spelling (and even then the latter is overlooked somewhat due to international users and all). Apostrohpes, commas, and the like are rarely poked at on forums and most of the time they're overlooked.
Simply put; so long as your posts are readible and people can get what you're saying, no one really cares if you misplace a comma, or whatever, and they go about their business of responding/reading. It's only when you're writing fiction or something else that requires good grammar that such things start to actually matter on a forum.
...Or if someone wants to make you look like a complete dork in front of everyone, simply due to trivial grammatical issues, whichever one comes first.