I didn't directly do it when adding the bash completion script auto sourcing because we don't know if the user is using bash or not, this sourcing could have some strange outputs in non-bash.

hmm, that's a good point.

should we perhaps add a bailout to bash_completion? or should we revert this change?

I prefer to move it to another codeblock with explanation that only users under bash needs to do that.

Sounds great; want to make that PR? :-D

I thought we mentioned it here already: https://github.com/creationix/nvm#bash-completion, maybe don't need to duplicate it?

Sure, either way. We can wait and see if people end up being confused.