I found out that the /etc/vim/vimrc.local is source by the /etc/vim/vimrc file. The vimrc.local has the option "set background=dark" which causes the font to be bold. It also forces bright font colors in vim. Since I don't use a dark terminal color schema I got problems reading.
So I wondered if this behavior is intended? Shouldn't the default config don't enforce things like color on the user?
It sets a setting that I have to disable/overwrite seperately in my .vimrc. I never set that option in any distribution, since it just used a suitable setting.
It changed my font colors and made everything bold. First I didn't know what caused this, then I tried to find a difference to Ubuntu (where it's not set). I searched many different files and then I disabled those settings.
I don't think that there should be such a setting for everyone, only if there's a sane reason, I don't quite see.
It doesn't "enforce" anything on you. Just change your settings in your .vimrc.