Methinks that the idea that "merit" is, an can be, measured in coin, or that "it’s nonsensical to have a market without money" is wrong. Money is the crudest approximation of worth (of course in the money exchange system it makes sense, but human systems have multiple "currencies" that run in parallel with money; and the rule regarding those is that only a fool would exchange these for money). Likewise, rules and laws are the crudest expression of values; an individual's ethos cannot be determined (and only extremely crudely approximated) by how many or which rules/laws have they broken. Again, there are many invisible moralities flowing over the rules/laws, and they actually determine which rules/laws are OK to break, and when. The meanings of actions change with time and context. A preserved tweet from 20 years ago has not preserved its (original) meaning neither for the author nor for the public; its meaning changes with time both for the author and the public. A "fully preserved tweet" would have to capture all these changing contexts, and in the model you propose it should have its merit constantly re-evaluated, and the merit-fluctuations saved (so that, you know, I can bet on this blog post becoming more valuable tomorrow than it was yesterday, regardless of what I think of believe).
IMO a system that is built for stability (encoded in the blockchain as an "unchanging/unchangeable" thing) is bound to be subverted in extremely weird ways and/or collapse because by design it doesn't take into account the dynamics of societies, which are, it turn, quite hard to predict. (Or, rather, taking into account all the subtle changes would make it big, unyieldy and hard to operate: for, to determine the value of your post for me *now* it would have to figure out to what time am I referring to when I think about this post (ie when I first read it) and then try to predict whether or not after writing the comment, the value of the post has changed for me; if I would have paid 10 cents for reading it the first time, how much I would pay to read it again? In 10 years' time? - this is a stupid example, of course, but the same would go for software, books, movies, ads, sports events, you name it.)