Just to emphasize that the correct answer to the above quote was provided by SquirrelJulietGarden. Merits do not shorten the waiting time between posts in any way, but rather the only parameter that does is Activity, as depicted in the said answer. Merits primarily contribute towards Rank alongside Activity, being the former normally more difficult to increment than the latter in general terms.

One more thing to consider is that the wait time between posts is also influenced by other things you may do on the forum. I can’t recall the complete list, but one of the main ones is performing a search: when you search, the wait time applies to both the amount of time you need to wait to perform another search, and the amount of time you need to wait to create a post.