If a compatibility issue is solved by providing alternatives or fallbacks, the issue shouldn't be listed in the panel or only those browsers that are not covered them.
column-gap is used together with
grid-column-gap in a CSS rule for grid layout, basically all browsers are covered, so it neither
column-gap (as not supported by all browsers) nor
grid-column-gap (deprecated) should be listed.
-webkit-background-clip are specified in a CSS rule, all browsers are covered and they shouldn't be listed.
width: max(20vw, 200px); is specified together with
width: 20vw and
min-width: 200px;, the latter two cover older browsers while the former declaration covers the newer ones, so
max() shouldn't be listed. (It isn't anyway, but that's because of bug 1636301.)
Of course those rules would have to be created and maintained manually and may quickly get complicated, though this ensures that only valuable information is shown to authors and avoids cluttering the UI.