Ah, but what about a man claiming to be the reincarnation of a moon princess?
You know, I didn't even think about the cases where the 'reborn' person might have a different gender than their 'reincarnated soul'. Now I'm scared....
Also, just a thought I had right now, maybe it can give Mode some ideas for her next try:
This time you went in claiming to know all the details about your 'soul' (I'll just use this word for now to refer to the 'reincarnated person', okay?), and that got you attacked easily.
Now I was thinking, what if you went in as someone who has dreams/ visions/ etc., but can't make anything out of it and now wants to ask people for help that are in a similar situation, so that in the end THEY will be the ones to make you an otakukin.
So, for Sandy she might have described those scenes from Gensokyo she saw, but since she doesn't know Touhou or anything similar she couldn't make sense of it. Now if people try to help her they inevitably have to come to the conclusion that her 'soul' is Ran. Now it would be a lot harder to dismiss someone as a troll whom you helped to find their 'soul', right?
As another example, let's say I barged in somewhere saying 'I'm Jack the Ripper', that would easily ge me dismissed as troll. But let's say I came in and said 'I'm having dreams of killing people. I'm scared, help me'. That might get someone interested, so I continue to tell the details of the dreams. How they can't be in modern times, what the clothes of people look like and so on. If all goes well, the end result would be someone screaming 'Oh my god, there is no other possibility, you've got the soul of Jack the Ripper'. Dunno if I'm just being too optimistic here, but that's how I can imagine it.
Ah, and there I go writing walls again. That always happens once I get curious about something (x_x)