Is there any badge for merit sources, or some plans to add this in future?
No, there's no badge for merit sources, and there's probably no plan to add this;
there's a huge difference between showing up in a "list of probable merit sources" and having a quote out there of you basically saying "I'm a merit source, come beg me for merit, complain about every merit I send, and accuse me of being part of the anti-X/pro-Y conspiracy."
The list of merit sources is also not made public, it's a voluntary position and there's no need to expose them to scrutiny, anyone paying attention would likely know who they are eventually, but the spammers are not really doing that.
I agree with everything you said, Upgrade00, and I will elaborate by mentioning that theymos had specifically announced that it was not his intention to announce merit sources because he did not want to encourage merit begging (or excessive merit begging, if there is a difference?).
But, surely one of the better threads on the topic of attempting to suss out who may or may not be a merit source (to the extent that they have not admitted being a merit source) has been maintained by
Coin-1 through the past couple of years. It is called:
[TOP-200] The most generous users giving meritsMaybe the name of the thread is not exactly literally accurate, but it is still an interesting thread that largely seems to assign a creative approach and a convincing degree of confidence to which members are considered to be or are not merit sources. By the way, Coin-1 has been doing a great service to the forum to provide this information, even while source members still can attempt to maintain some plausible deniability, unless some of the source members have actually admitted to their source status (but still, plausible deniability in terms of any time that source status could be removed)...
By the way, one of my own funny stories is that when merit source status was first announced, I was confused by the whole thing, and I had read theymos's assertion that he was not going to announce who were the merit source, and asserted that members will likely figure it out with the passage of time, but then a few posts later, he was finger pointing at me, even though I have never really completely admitted to it, except for just proclaiming that I know things about my practices in regards to smerits, and maybe some other quasi-incriminating but attempting to be somewhat vague admissions.