The comments in the release notes point out that those using e.g. v 1.91 will cause false decodes and are therefore considered as QRM. From the other side, those using 2.0 Rc4/5 or final with the extended features (which which could be useful for transferring SOTA data as well as contest info) will not be decodable by those using V 1.91 and hence seen as QRM from their side.
So as you say there seems to be a split in the community and as the later RCs have moved back to the “old” FT8 frequencies, this is going to be a difficult time.
V 2.00 RC3 is the “sweet spot” as it can talk to both the old and the new protocols.
Compton - if we believe the release notes, RC5 IS the last test version and the full V 2.00 version will come out soon. We’ll have to see what the take-up is on this version vs sticking with the old version.
I wonder if any “back-door” was built into v 1.91 so that it can be disabled - now there’s a conspirary rumour started …
Please don’t shoot the reporter!