Imagine if Theymos decide to rollback all ranks counting only the earned merit so far, should be fun.
It would be insane. Because, a legendary is contributing to the forum far longer than the merit system exists. It is very much possible that a hell lot of posts created by him/her in past were worth of merit, but it were not awarded any. Now, if only the earned merit is considered, it'll be highly unjust to the old posters.
For example, there was no merit system in 2014. But, if
this thread was created today, it probably would have received some merit. This is how many of our old threads are merit less, because they were created way before the merit system.
Looking at merits earned and merits received (airdropped) before the January 24, 2018 introduction of this new merit system are two different indicators based on different presumptions. Of course, on a general basis there are a lot of threads and active posts that have not received merit for their posts prior to the introduction of the merit system because only a few members are going to go back and use their merits that way, and of course, some exceptionally notable historical posts have still received a decent amount of merits and attention drawn to them for such purposes too.
There is no injustice going on but just an overlap of two systems and some lack of consistencies, which is largely how th world works, anyhow. Merits are not a reflection of objective goodness, even though there could be some of that going on, but there is also human subjective element going on too, as well as whimsical irrationality.. and sometimes not so good sides of humans shown through their use of their smerits.
Of course, merit sources are held to a bit of a higher standard, but even then various irrationalities and whimsicality still might exist and might not go beyond theymos's level of detection or tolerance.