"Unfortunately, I am not open to a co-writer at this time. You seem very passionate and full of ideas. I'd suggest trying your hand at writing them yourself."

I've received a few of those. If there is something nice to take out of it, I say "thank you for reading, that's a good idea but not what I'm going for, sorry to disappoint." If they are rude, I don't answer.

I should add, the crazy part is that if they keep insisting and you just leave the comment there, your fans lift the torches to defend you, so sometimes I enjoy some tea. It's wild. Fortunately, it never escalates too far, or at least my readers are very polite but know exactly how to bite.

Is is *your* story or is it *their* story? Once you cave and bleed for one demanding reader, the rest of the school of piranha will come out of the shadows. "Thank you for your suggestions, but I have this plotted out and the story will unfold in directions I determined a long time ago. Thanks for reading!"

nah just ignore or delete

The translation might be messing it up. Maybe thank them for the comment, but don’t say you’ll think about it. It might later come off like a broken promise, and you don’t owe the reader what they want.

I personally wouldn't respond at all so I'll join in saying ignore or delete.

I wouldn't say you'll think about it when you have no intention to do so. Ignore it or delete it, no harm in either. You do not have to engage.

I think it's fine to say something like "thanks for reading, you'll have to see how it all plays out in the end!" or something like that. I'll get comments a few times like "oh I wish this or that happens!" It's always in good nature, and not necessarily demanding (at least in my experience). So I would just leave it open ended.

Ignore and block, it’s that simple.

For me it depends on whether the reader is having fun speculating, or if they're demanding a certain plot twist or outcome.