Ideally you would be able to link your (say) github and WMF account.
So that if I (as an outsider) start a bug report/patch/etc using my
existing github account, and then eventually get a WMF account (so
that I can do labs-related things?) I can manage my bugs/patches
regardless of which account's cookies happen to be on my machine.
Then you might plausibly allow 3rd party accounts to open bugs,
comment on them, etc, but require a WMF account in order to +2
patches, resolve bugs, or other higher-privilege operations. It
should be as easy as possible to open and link a new WMF account when
a new user starts wanting to contribute more.
--scott