Sentence discussions for source sentences of fewer than x characters get appended to random other discussions

Bit of an odd one, but for some reason if the source sentence is fewer than x characters (I seem to recall the threshold might be slightly higher than 15 and fewer than 20, but I’m not completely sure about that), the sentence discussion gets appended to a random existing discussion, which is not even always a sentence discussion.

A couple of examples of this, but we have seen it occur more often:

Interestingly, it seems it’s not even a question of creating them, but also merely when trying to “view” them, as reported in the latter example above.