@jessel what does "support groups natively" mean to you ?
There are Group objects in the ActivityPub vocabulary already.
Posting to a group is already covered by well trodden interactions.
With a little charity with regards to the interpretation of some other vocabulary activities we can say that joining/leaving a group are also there.
What more do you think is needed?
@julian I think URL comparison should not be done as a string. Like @silverpill said, fragments are stripped before comparison, alongside the usual other considerations (normalized query parameters, UTF and case normalization for the hostname, etc)