There are a few non-editable columns available in the tag editor. At least there are "Duration", "Track gain" and "Album gain".
It would be great, if they were shown in a different color - similar to the artists column, when it contains multiple artists.
I'll see if I can normalize the UI for the next release.
Well, the artist-cells are indeed different than duration and gain - but they're also different than title and album...
But nevertheless you decided to make them look the same as long as they're editable and only look different when they're not...
So why should there be only one kind of editable cells, but two kinds of non-editable?
Possibly future change. The controls are really of two different types since artists a re partially editable, depending on state. The other cells are never editable.
Well, now we have two styles for non-editable cells... I think it would be better to use only one of them.