Should be karma based.
I think it should be both, but otherwise this suggestion doesn't contradict
previous discussions about karma requirement for higher ranks as well. It'd be worth testing the waters in the senate with a few options (based on different suggestions that were made) in order to
force try and make change happen in that direction. We've had ranking difficulty increase a few times before, so it's not that controversial, but otherwise the results of this could be dramatic.
For example I think in hindight something like 1/10/100 (Senior, Hero, Legendary+)
could work, whereas if you were to apply some sort of higher thresold
like btt at 100/250/1000 as you've suggested, then this would effect seemingly most user ranks and I can't imagine ever gaining consensus in the senate (nor with the community for that matter). Already a threshold of 100 karma for Legendary would cut these by over half, based on
170 Legendary with 100+ karma (corrected), and otherwise
458 users with 1,000 posts (obviously less with 1,200 for the rank). At 1000 karma, there wouldn't be any Legendary users at all, so for me this is a non-starter proposal.
I'm not sure this change would change anything.
Otherwise, what is the difference between Legendary and Mythical rank?
Not much directly though, it'd just be more logical per original reasoning. The suggestion of shifting Mythical and above to lower requirements I like the most, as it would make the
6 Padawan members Jedi's and 8 Mythical members Padawans (which based on the users in question, I think is pretty fair). Not too many XX number of Legendary members into Mythicals, but a lot of Legendary would be closer to a new rank at least.
(Part of reply removed as off-topic)