At the moment, after one has matched their album/recordings, with the corresponding album/recordings from MusicBrainz; The bottom panel has columns "Tag", "Original Value", "New Value", and cover art. If a tag is modified (different between the local copy in the audio files, and the data from MusicBrainz) the data appears in yellow.

The user needs to spend a lot of time looking back and forth between the New and Original values, to try to see what has changed. Many times it's simply a typographic apostrophe, or a hyphen vs. an en-dash, or worst case, a "l" vs. "I" character, or some accented character is normalized in Form C  vs. Form D and completely indistinguishable visually.

Picard could make these string modifications much easier to see for the user. Perhaps a red squiggly underline. Highlighting with a solid block of color might be confused for certain emoji? Being able to see the raw UTF-8 octet values in hex would make it possible to distinguish between different normalization forms – or even better, just have Picard display the encoding and normalization forms of the "New" and "Original" values itself.

(I think maybe 80%~90% of the differences I see are just Title Case vs. sentence case, whitespace, and apostrophes. The rest are usually very different strings, which require manual investigation. But, squinting at some yellow text on a white background, and looking back and forth to find the differences is way too much work to put on the user.)

Oh yeah, and another thing: 80% of the time, the difference is in the title and artist, where the Original value is: "Song Name (feet. Artist)" and from MusicBrainz, the New value is: "Song Name" with the New value for the artist something like: "Band feet. Artist".

It would be nice if Picard could make it easy to distinguish between the standard MusicBrainz Style artist and title string cleanup, and when there's actually a typo or something which the user/editor will need to research and possibly correct on MusicBrainz. 

So, make these kinds of modifications be a lower priority/concern for the user:

• First letter of word capitalized or lower case
• Typographic apostrophe, prime, double prime, and dashes
• Featured artists, as long as the artist name (and copula?) has moved between the title and artist fields
• Form C vs Form D unicode normalization, maybe?

But make these kinds of modification be a high priority (visually clear) for the user:

• A change of one or more characters to anything other than the upper/lower case version of that character
• Someone mixed up the letters "А", "Α", and "A" (Cyrillic, Greek, Latin)
• Extra or missing whitespace (It may be important)
• Extra or missing text
• Case differences in the second, third, fourth, etc. character(s) of a word.

If I can quickly tell at a glance whether or not there is an error in MusicBrainz or someone just hit the "Guess Case" button on MusicBrainz, that would save me so much time. (or if, you know, "Guess Case" guessed wrong, and so I need to fix it anyway.)

(I'm tagging FLAC files downloaded from Bandcamp, but not every corresponding release was imported directly from Bandcamp into MusicBrainz, and I've been finding a lot of small differences.)