I think the lookup formula should have a setting to show only unique values. I know ARRAYUNIQUE() in the rollup formula can do the same thing, but this is better used for complex operations. Also, colors will be lost here.
Huge second on this! Would be great to retain the colorful tags and just have a switch to flip that would show only unique tags rather than repeats. I hate losing the visual richness when I have to swap over to a roll-up.
Double bonus if this could also apply to linked field look-ups! If Record A is linked to records B and C and records B and C are both linked to record D, it would be great if I did a look-up from record A to that link for records B/C and it didn't double-display record D!