I made a bug report about this ages ago and subject has apparently been discussed and decided long ago, but I'll just make this plea to the visual design group to have a fresh look at this.

The little triangles on table columns showing asc/desc sorting order are the opposite they are everywhere else (as far as I know). To make matters worse, this appears to depend on gui toolkit. On Muon ^ is smallest first and on Dolphin it's largest first. This renders sorting indicators nearly meaningless. You'll see which column is sorted, but you have to deduce from content which way it's sorted.

I get and respect that those icons used to be arrows, it made sense then, and developers like them as they are, but could this be a setting somewhere?

While at first I'm inclined to just blame Muon for getting it backwards. However, digging into it some more, I found the following UX questions which suggest that there's some controversy, but generally suggest using /\ for A-Z (A at the top) and \/ for Z-A (Z at the top):
https://ux.stackexchange.com/questions/ ... ble-header
https://ux.stackexchange.com/questions/ ... te-field-h

Which implies that dolphin, kmail and most other things are getting it backwards.

Thanks for those links airdrik. Amazing how many different mental representations people can have for this. Mine has always been that the triangle is like a silhouette of a stack of physical items. Pointy end up ^ means smallest item on top.
For some reason, I don't seem to encounter other implementations anywhere other than in KDE software.

I cannot believe we are now in 2020 and this issue is still present