I know why the 50 reputation requirement exists. Mainly to prevent spam and unhelpful comments by new users.
My issue is: When I come from other Stack Exchange sites and collected some reputation there, I am apparently not a bot and also know how SE works. But I have to start all over again, which is frustrating.
I am currently trying to use Linux, so I created an account on Ask Ubuntu and the Linux Stack Exchange site. An answer that was posted there didn't work, and I wanted to ask for additional help, but I couldn't comment. Opening another question would probably lead to a duplicate. I am also bugged by the suggestion to go find some other questions and earn reputation first, since I need the help now.
So the only option left for me is to go to a forum and ask my question there, which I don't want to do, but I am implicitly urged to do that.
Unlock comment privilege for all sites either by getting it on one (or a specific amount of sites) or according to your global reputation, which would be the accumulated reputation amongst all SE sites, and require maybe 200 global rep.
What do you think?