I still haven't gotten around to creating a Manual of Style so there aren't any confusions like this, but there are some exceptions to the trivia. We do add some out-of-universe trivia as long as there's either (or hopefully both)
- a credible source, or
- an obvious direct correlation. (In this case, we also usually add something around the lines of "Though unconfirmed..." to show that there isn't an official source that directly credits the correlation.)
In the case of the Pai Mei article, it seems obvious enough (to me, at least) that the character was most likely inspired by the Kill Bill character - which also has some extra credibility because it's a film that pays homage to martial arts. The same thing happened with the Lu Kang character, which is why we have out-of-universe trivia on him. So I went and added the info back into the article.
Just as a counter-example, here's what isn't an exception: We keep rejecting the trivia that says Tong Fo talks like Christopher Walken because there is neither a source nor a strong enough direct correlation. Sounds can sometimes be misleading (especially in voice acting), so any kind of connection it may have isn't obvious enough. But written names and most images cannot mislead, and therefore have a stronger correlation.
Sorry again for the confusion. This kind of specific detail with this wiki's articles isn't written down anywhere yet, and I take the blame for that...