I don’t even know why this is a hypothetical question in the first place. There is no rule against this but I don’t see the point. It’s scummy (as pointed out above), it’s a waste of time and there’s no merit in DevForum stats aside from feeling good about yourself. It says nothing about your credibility, chances towards promotions or anything at all.
It is often (or all the time) falling under what is commonly called “unspoken rules”.
And yes it is frowned upon, and I belive you aren’t allowed to have an alt on the DevForum, but using a friend/colleague/family relative or whatever to like your own posts is considered “shilling”, which is also frowned upon.
Just to make it overly clear: yes, you will get reprimanded for any abnormal forum usage like that. The forum rules topic does not contain an exhaustive list of rules, and you are expected to use common sense beyond that for cases that are not specifically described but should be regarded as obvious.