To get a little bit back on topic here:
I am genuinely interested in a real discussion on this very important matter since now the DT is directly a merit dependant system.
I don't see a problem in spending Merits for posts that are similar to your point of view as long as they offer any additional value to the reader. In sections like Meta / Reputation it's always a matter of opinion because the topics need a point of view like is it correct to do a or b. Either you agree or you disagree and a bad suggestion /
an insulting post is not worth a merit in my opinion.
Posts in Meta / Reputation are totally different compared to a guide how to use BTC or something else. It's like in school when you have to do a math test and and an essay. It's easy to figure out the quality of your math test (if your calculations are correct) but not very easy in an essay. Your opinion may differ completely from that of your teacher but finally he is the one determining your mark.
And it's quite normal that people give merit to other people on boards where they are also writing posts themselves. Usually, everyone has some preferred boards to read and write and sncc made a great post about it in May 2018, long before Merit was tied to DT power:
https://bitcointalk.org/index.php?topic=3650124.0You can read his entire post, I'll just pick a visualisation that it's totally normal to have some preferred boards:
Purple = Meta / Reputation / Scam Accusation...
Green = Wall Observer
Blue / red / light green = Russian local board
Black = Indonesian local board
Orange = Turkish local board