Subscribing to mailing lists and posting
For all the lists we care about, you can get the posts from http://news.gmane.org/
They will be under comp.compilers.llvm, comp.compilers.clang, comp.gcc, ...
You can subscribe to them with a newsreader and form your mail program, reply also.
Just set the list to not deliver any email and you can read it all from the newsread.
In thunderbird mail program, you can add them with file->new->other account->newsgroup and the newsgroup news.gmane.org .