Is it possible to search for all the posts with the most merit?
I don't see this option in the
Advanced Search.
What are you trying to search for? Merit is not a measure of publications' reliability or quality, so relying on them may give false results.
There is no official way to do this, use some Userscripts --->
https://bitcointalk.org/index.php?topic=5148488.0If you are trying to use it to link accounts or abuse you may need more information, unless one of the parties is a Merit Source.