I like the semantics and the increased consistency.
I don't think we use the combination of --bold --underline anywhere else yet;
it might look a bit too dense (ignore the underlined > obviously)

Maybe that's an appropriate amount of loudness for overwriting an existing file, but seems a bit much.

Looks like your theme doesn't use --bold in fish_color_redirection like the default one does?
That's probably better, so maybe we should change the default themes accordingly. Redirection should probably still be different from fish_color_param. We have some underline styles available now, which we can use on most terminals

Looks like your theme doesn't use --bold in fish_color_redirection like the default one does?

Yes, my theme contains set fish_color_redirection normal, but I don't think the default theme needs to be changed. In the foot terminal emulator, the bold+underline combinations looks good:

I think this is ready to be merged once CHANGELOG.rst has been updated.

which font settings are you using?
I think my screenshot is with font=monospace:size=12, mostly foot defaults and

$ fc-match monospace
NimbusMonoPS-Regular.otf: "Nimbus Mono PS" "Regular"

nevermind, it was just due to 1.2x fractional (compositor-level) scaling on my end, so it's all good