Using the occasional "lol" can't be that much worse than using incomplete sentences and absolutely no punctuation, can it?

As you have pointed out, you get upset by people using chat-speak. However, you also get upset when people nit-pick about poor grammar usage. Perhaps it has not occured to you, but chat-speak is a form of bad grammar.

At best, chat-speak is irritating. At worst, bad grammar is impossible to understand.