I have trouble making work together "one of the best of the team" and "one of the most exhausted". It seems weird to me that the "best" persons use a tool that so obviously drag them down (don't they realize they are more exhausted, slower and make more mistakes at the end of the day?)

I believe that there may be some post hoc, ergo propter hoc at play here.

For instance did you include the age of the persons in your observations? It wouldn't be surprising that the persons choosing vim are a bit older on average, and then one could think that they have a bit less stamina and are exhaust faster?

Or maybe they are actually doing more, like spending part of their energy helping others? That's also a pattern you can see often in group training sessions.

Also, you mentioned that you won't help them with the "weird issues" they usually have with vim. Do you apply the same treatment to non-vim users?