My theory is that the so-called "Reimu" is nothing more than an AI unleashed on /bant/ by none other than Abib, with Hiroshimoot's full backing.
What this AI's purpose is will forever remain a mystery, but we can look at the facts that indicate its true nature. Notice, if you will, how the still-crude algorythm is only capable of generating (besides the basest of them) the same set of replies, no matter what the flesh and blood users of this board may post. Moreover, and this besides the few glitches that you could observe these past few days, the AI "breaks" in certain instances when the algorythm cannot find enough keywords in a post to generate a response to it. In addition, I would argue that those who systematically show up in these AI-generated threads are its testers.
Nevertheless, it is evolving and I think it safe to declare that, as long as it keeps doing so, the "Reimu" AI will not be withdrawn from /bant/.