>Why does the built-in MIME type detection code that gets called if no MIME type is specified (Zotero.MIME.getMIMETypeFromFile() and friends) not suffice here?

>There's no reason this should need to be done in individual translators. Is the built-in functionality not working?

If I'm understanding this correctly, that would result in a doHead request for each link? Seems rather inefficient to me.

While MIME type mapping is not, per se, required for this, there might be translator-dependent logic based on different MIME types (file extensions in this case). E.g. in the NPG translator I said
>I disabled attachment downloads for item types that we can't recognize. This was mostly because I saw that videos were not direct links, but links to web pages with embedded video player. So we don't want to take snapshots of those. Instead, now we just attach unknown files as links. See last test case for this.