Ok, taboo "make an ass of oneself".

Fair, but difficult. After some thought I'm going to replace it with "accidentally make an inaccurate highly-negative impression." That seems to distinguish failure modes that are innocent but embarrassing from those that might actually merit exclusion.

Yes, and one may very well decide that one's go game is good enough and that further improving it is not worth one's time compared to doing other things.

Funny you should put it that way -- I made more or less exactly that call with regard to social skills long ago. It was lurking here that changed my mind.