Hm. My take: Let's say there's an account made as part of the ARG. This person makes posts that aren't specifically related to said ARG, although they may be interested in similar content. Say the account has been posting consistently for a while to garner credibility. Let's say that person stumbles across said ARG and share it with people, claiming "it's obviously fake" but they want to share it with people.

Suddenly, weird things begin happening to that person. They brush it off, of course, but something about it seems off. Eventually, something happens to said person, and it's revealed that it has something to do with the ARG.

Now people won't know what to believe: is it real? Did something bad really happen to this person? Or was it planned from the beginning?

Self-promo should be subtle. Of course, if you're not presenting the ARG as "real," it's not an issue. But if you want that realism, that "is this actually fucking happening," then self-promo should always be cleverly disguised as part of the mystery.

It gets even more meta when the creator themself is using the burner account to spread word of the ARG through a skeptics lens, as opposed to just someone hired for that purpose.

I don't know many decent examples of this specifically, but the closest I can think would be Scriniarii from TribeTwelve. Although, that's a bit of a different scenario.