[Wilfred]

JSON and CSS are supported today, and I'm interested in adding more structured text formats.

If a format has a tree-sitter parser, it can be added to difftastic. The TOML tree-sitter parser looks good, but there isn't a mature markdown parser for tree-sitter. There are other markdown parsers available, so in principle difftastic could support markdown that way.

The display logic might need a little tuning for prose-heavy formats like markdown though. I'm not happy with how difftastic handles block comments yet either.

I'm not sure about formats that contain more prose, such as markdown or HTML.

[zmix]

I think supporting XML would be something, a lot of people would appreciate. That XML is difficult to diff comes up again and again... However, one would need to decide, whether one wants to compare by syntax or by meaning. Latter one may be preferrable, but would require the XML to be canonicalized on both sides, first.