Sorting on comment field not ordered as expected

[tbm72]

When viewing my library in the main Music node I've added the Comment column to the main display. If I then sort my library based on just the Comment field it's not appearing as I expected it would.

Some of my tracks have comments in that field but the vast majority don't. I expected that a sort on that column would show either all the empty field tracks first or all the tracks with comments first (depending if the Comments column was sorted Ascending/Descending).

But what I get is about 100 tracks at the top with nothing in the Comments field, then all the tracks that have comments, then all the rest of the tracks with no comments. I've double checked that the tracks displaying at the top of the list definitely have an empty comment field and the sort order is only using the comment field.

[tbm72]

Edit: My mistake - I think there were some invisible tags somehow in the comments field (almost like a tab escape key) so they looked empty when viewed in MM but there was something in there that I could only see when I opened the tracks in mp3tag. Weird.