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You seem to be confusing Merits (those that are awarded to you, that are visible on your profile, are non-reversable except for extreme exceptions, and count towards your rank and other situations such as DTs voting) with sMerits (those that you can send to another profile, and that are derived for the most for every two Merits that you receive (generating 1 sMerit), with the exception of the initial airdropped sMerits and Merit Source sMerits which are generated centrally by the forum).
You are therefore out of sMerits, not Merits (you have 252 –> 250 airdropped and 2 received from two different people at some point – they sent sMerits, you received Merits, which in turn generate 1 sMerit in your balance for every 2 Merits you receive).
In order to rank-up you need to, for the most, create decent content and wait for someone to spot your posts and merit them.
Since we’re on @nakamura12’s thread, he serves as a perfect example of how one can rank-up (in his case he needed 100 merits to do so), even if it did take some persistence and time to get there.
Buried posts have some safety nets they can default to, such as those threads that exists on Beginners & Help and Reputation, that allow you to report/self-report them in order to get them reviewed. That is though a rather exceptional method.
Topic starters may get merited frequently, as they are the ones who are bringing something to the attention of us, and if it is well argued it may deem meritable. The same goes for any answer or contribution in that thread, although normally what catches the eye first is the OP, and not everyone reads all the thread to the end. In addition, often there are very similar answers, and perhaps that may reduce the meritable answers to just a few.
After some time, revisiting a thread may not bring the same enthusiasm as when it was created, so there is that factor that could at some point influence the number of readers of posts that are aggregated in late positions. That really will depend on the liveliness of the thread, and as I stated before, on the repetitiveness or uniqueness of the contributions to a given thread (there are some clear exceptions of long lively threads).
