I think people know what it means, but the bigger issue is that a lot of non-native English speakers do not parse nuance very well, and might not understand that the term in itself is somewhat strong.
I've heard a lot of foreigners (especially people from nordic countries or germany) speaking English in a way that is a lot ruder than they might realize. One thing is the personality (they seem to be more direct), but there have been many instances where it's obvious they aren't aware that the language they're using is way too strong for their situation. This goes doubly so if your main English education is internet forums.
Not saying that it's a reason to remove GTFO, but the humor (which is slightly in the very exaggerated vocabulary, which seems to be misinterpreted as a strong intent) is probably lost in translation.