I don't know if someone else already asked something like it but I'm new in this community and I think that it could be a good idea to create generic reputation for some privileges.
For example, for me it's not possible to comment on Stack Overflow and not in Super User.
Some privileges must remain limited to the section where the user has gained more reputation, for example the voting privileges, but some privileges should be "generic".
What do you think about this idea?
P.S.: I tried to search if this had already been suggested but I didn't find anything, sorry if this is a duplicate question.
EDIT: After the Sarnold's answer I would change a little my question: If it is true that when a user, for example, has more than 200 rep on stackoverflow and he want to register on Superuser, it start already with 100 rep my question is: why don't create more privilegies that abilitate these privilegies without adding rep? Something like "Comments in any sites"...