I am the assigned ART directorate reviewer for this document. These comments
were written primarily for the benefit of the ART area directors.  Document
editors and WG chairs should treat these comments just like any other last call
comments.

I previously reviewed the -09, -10 and -13 versions of the draft and now reviewed the diff
between the -13 and the -15 versions. The added text about the ability to reinitialize 
the group changing the protocol version and/or ciphersuite addresses my concerns.

The issue of inability for a client to remove itself from the group by its own 
seems unsolvable in the MLS architecture. While I think this issue is important, 
I'd leave it on ADs' discretion.