Yes, you can merit yourself but you would need two accounts for it. A lot people do this on the platform and they get away with it. People own multiple accounts and once they get merited on one account, they send that merit to their other account. This is very unfair because it denies other people who actually deserve the merits.
While it is possible to merit with an alt account, doing so is not recommended.
If you look through the Reputation board, you'll notice that there are threads open against those who were caught in the act of self-meriting their own posts using their alt account.
I agree, however, there are many people who do not see this as a problem. Recall the famous liar naim027 and how he exchanged merits with his alternative account Dic3L0v3r.
Since the user cannot deserve himself, and it is not possible to do so, of course, opening a second account can easily solve this problem. Moreover, it will always be a moot point whether to leave him tags or not. I think this statement from the admin says very well that the exchange of merit is not a big problem.
If a DT member tags you for something stupid involving merit (ie. probably anything less than selling merit), then they're not going to be a DT member for much longer.