Some other UF addons (Aguf for example) only show the buffs you cast on your party members next to their UF. This is very useful for classes that need to constantly buff their party, like paladins for example. As they don't have to look through all the buffs on their party members to see if theirs is still active.

I was wondering if this functionality could be added to LUF?

Really? I wonder how Aguf only shows the buffs cast by you on party members, and nothing else (besides debuffs) next to their unit?

I would love if Luna could somehow have this functionality in the future, it's customization and raid frames are much more superior to Aguf.

I would also love the option to show it over a raid frame and maybe be able to only show when missing. also, option to hide when in raid group would be nice as I use raid frames for party

In vanilla you can't distinguish between your own and other buffs/debuffs.

They don't. Its a classfilter.