There are already gmane mirrors, such as: http://news.gmane.org/gmane.comp.python.devel
Do you use it yourself for thread subscription?
I don't think there's any "thread subscription", if you mean subscribing to individual threads.
My point is that gmane mouse clicking interface is insane. They can not fold quotations.
Neither can some e-mail clients. It's up to posters to quote (that is, strip quotes) properly. Gmane also allows you to use NNTP, though, perhaps you can find an NNTP client which has the desired quoting UI :)
And if you'll look attentively you won't find most of messages from ongoing discussion about bootstrap script for package management.
Yes, gmane seems to have some strange "duplicate suppression" algorithm which doesn't go well with cross-posting.