np!

I didn't realise it happens when the column gets too narrow. That's fine, I'll just make it wider then - thanks for the tip!

The rating tooltip only appears in the column tracklist view ("List") when the Rating column is too small to preview the full 5 stars. I don't believe it's something you can override in a .less file, because it's integral to the column tracklist view (It does the same thing for every column).
If you do prefer to keep the Ratings column more compact, but don't like the tooltips, try the Numeric Tracklist Ratings addon: https://www.mediamonkey.com/addons/browse/item/numeric-tracklist-ratings/

Also it seems to be dependent on the view I'm using to display tracks. If I first click on one of my playlists and hover over a track's star rating from there it shows the star rating tooltip but if I go directly to an album and then hover over the star rating it doesn't appear.

Also happens in some other skins, eg Dark Monkey.

I use a slightly tweaked version of the default Material Design skin and in one of the more recent MM updates I noticed it now displays a tooltip popup when I hover over the star rating:

[url=https://ibb.co/ZzxF7bt][img]https://i.ibb.co/ZzxF7bt/Untitled.jpg[/img][/url]

This can make it a bit tricky to actually click on the star rating itself as the tooltip gets in the way. I figured it must be something small in the code of my custom skin because it doesn't do this in the default Material Design skin. So I tried creating a clone of the default skin with no changes made but it still shows the tooltip there (although not in the actual default skin if I switch to that).

Firstly I can't really see why it shows the tooltip in a cloned copy of the default skin but not the default skin itself and secondly is there a way to target the star rating's tooltip attribute in the skin_custom.less file and hide it that way?