Users will then delete previous posts if they do not want to rank down. Easily circumvented.
By mentioning about activity point, I meant actively posting. People can keep posting for their signature campaigns or bounties, and delete their past posts to maintain (nearly) constant activities over time. However, I don't think that is big issues and unsolvable because what LoyceV began to collect weeks ago might help, and forum can do it too (
Viewing unedited posts and deleted posts)
It is fair if old Legendary maintains that rank over years if that account is inactive posting, but if that account makes 1000 posts and does not satisfy merits required (ie. 100 merits), that is very good indicator for shitposters.
A better approach is to demote the people who do not distribute the merit to others. Those who receive merit gets smerit too. They should spend it too.
They only should send their sMerits to good posts they see, but they must not do it.
Legendary: 111 out of 1602 (>= 60 earned merits in last 6 months) --> 6,93%
Hero Member: 116 out of 1865 (>= 48 earned merits in last 6 months) --> 6,22%
Sr. Member: 82 out of 3321 (>= 42 earned merits in last 6 months) --> 2,47%
Full Member: 116 out of 6167 (>= 30 earned merits in last 6 months) --> 1,88%
So, there are 12955 users from Full members and above; and only 425 of them (about 3.3%) satisfy the proposed time-rolling merit requirements to maintain ranks (by DaveF). If that thing actually used, it will be another big change of forum, just after merit system in 2018. Personally, I think it will be the biggest change in forum rank system, because all ranks will be affected, no matter users are old-era (before) or new-era (after the birthday of merit system).
Legendary: 111 out of 1602 (>= 60 earned merits in last 6 months) --> 6,93%
With legendary users who have been actively posting within last 6 months, and earned less then 60 merits; are they real legendary users? There are hundreds of users from Full Members to Hero Member ranks whom earned from 100 merits and above to rank up. They likely have higher values than those legendary (less than 60 earned merits) during the same period of last 6 months. I believe for those cases, their earned merits are much lower than 60.