First off, MG and by extension G3-internal CF are really wonderful, very useful tools (although CF seems buggier). I often wish I could filter by change type, so I don’t have to go through glyphs that only got different color, or see only the glyphs with changed spacing.
Speaking of spacing, if it changes, all the outlines are marked as changed too. All the x coordinates change with a different LSB so it makes sense, but is not terribly useful. Maybe there could be some logic that if spacing was changed by 20 units and all nodes were shifted by 20 units then it’s clear that only spacing was changed?
The overlay also doesn’t help much in this case, because it shifts. And then it’s especially tricky to see if the outline was actually changed too, so you have to go through node coordinates. I wonder if it could overlay outlines aligned at the lefmost node or something like that.
Also, when e.g. a file has a few masters, in both panes Light masters are selected; you want to compare Bold masters and select it one pane, there is a slow moment where everything is compared and is found different, because it compares Light and Bold. I wonder if there can be a delay when comparing starts after switching masters or a dedicated button to start comparing.