Yeah, I know the sort you mean. There's one who does that over on the UD forums from time-to-time. It did get quite silly at one point with an entire thread getting side-tracked into non-native-English speakers saying they couldn't read it (along with a lot of English speakers). They did sort of get the hint, and the posts are slightly more readble now, although I tend to ignore most of them, since they never say anything useful anyway.
Since you've already tried talking to them, I don't know what else to suggest.
