[@PKMNB0Y]

I don't think the motivation is all that difficult—Koishi's perspective was totally changed by her interactions with Reimu and Marisa on Youkai Mountain, and I think that she would be overjoyed to have an opportunity to resolve an incident.

Her ability has been shown to not be all-encompassing forgetfulness (otherwise Hopeless Masquerade couldn't have happened), so I choose to interpret it more long the lines of being gradually forgotten by anyone without any real connection to her. Given the length of time most indents are and the hope that it'll build some real relationships between her and the other 2hus, I had figured it would make for some interesting situations with NPCs without harming any interactions with the main cast. If it's still a problem, a magic forget-me-not could be used to write around it.

I can switch if you think it'll harm the story, but I think that ZUN gave her character enough slack to be included in incidents.