Almost certainly. Calibre seems to be able to convert just about anything text based into whatever format you want, in a very batch-friendly way. And it's certainly not the only tool of it's kind, though the others I'm familiar with are more specialized.

But first you've got to know that the other tools exist. And if they're already comfortable using Ao3's system, it could be one of those 'if all you've got is a hammer' situations. Though I'm not sure someone would actually have to make their upload public if all they wanted to do was use the downloader...

-IA.

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