A new language can give you a slightly different way of being funny, angry, or shy.

A second language gives you slightly different equipment. The jokes available are different, the ways of being polite or angry are different, and people often report being a marginally different person in each. It is not pretence, it is that the tools shape what can be expressed and therefore what gets expressed.

If you speak more than one, notice which parts of you only appear in one of them. If you are learning, expect the personality shift and treat it as part of the learning rather than as awkwardness. And be slower to judge someone’s character from their second language.