It's not (only) the marginal English - which you're right, is at least as good as my Spanish, French or Italian, and WAY better than I can write in any other language with or without a dictionary. (I gave up trying to participate in a French sportbikers' forum several years ago. )

It's that those people post statements of marginal relevance to 15-20 threads at once, often digging up threads that are months or years old.