That is one of the things that always got me, folks running around with stats like Int boosted to 8-9 permanently. Maybe my interpretation is wrong, but at that level trying to deal with normal people would be frustrating at best.
If you consider that 5 is supposedly the limit of purely human ability in terms of Intelligence, one would assume that would be true of even people with Int 5, given the frequency with which extreme intelligence seems to come paired with one sort of social dysfunction or another (whatever its source).
Since nobody's really interested in enforcing that either, it'd be difficult to make a case for doing it towards those with Int 8-9. There's also the argument that if you have enough Mind to bump your Int to 8 or 9, you also have enough Mind to recognize and adjust yourself not to suffer those dysfunctions at the same time. Edit: Which is one of the reasons it's so much of a pain to push for mental attributes provoking Disbelief. People are rarely using their Int 9 to do anything a normal person would actually disbelieve.