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I had thought it would be an easy matter to read the image comment first... if not then I suppose your options are quite limited.

Exempting Pixiv would certainly help.

Another possibility would be to give the user control over whether their upload has its exif data stripped. Whether the option would be used appropriately, I don't know.

I don't think I'll have anything more to add to this discussion, since I know very little about the workings of this website. It's not ideal, but with some effort I can probably work around this by storing "stripped" md5s at my end.

Thank you both for responding.