Ankiweb and AnkiDroid do not display images containing # (pound, hashtag, sharp symbol)

[dae]

@ShapeKeyes

The real question is if there is a way to rename all the offending cards at once

You can use Notes>Find&Replace to adjust multiple cards at once.

@ShapeKeyes

Windows changes it back to a # in the sort field, but the HTML text remains unchanged

This happens because Anki stores filenames without encoding on disk (legacy reasons), but needs to encode them before they’re shown in the editor.