But in that topic they don't talk about the colored stripes using the sidebars.

I've heard that some academies might use professor bars on colored belts other than BB to indicate that they are instructors. Not very common but apparently it happens.

Sometimes you’ll even see the red bar on color belts for instructors to go along with the side tape. Same thing, different places recognize their instructors differently

The entire thread is literally about the white instructor bars and red tab that the arrow in your screen shot is pointing to.

My former coach even had a blue bar instead of a red bar, ( after white bar on the blackbelt)which some people from the Royce Gracie lineage wear …

I’ve also seen a match on YouTube recently where Roger Gracie wore a plain black belt without any red bar or stripes…

I also have seen rare cases in which the people had a red bar instead the black bar already on blue, purple and brown🤷‍♂️, which shows they are in kind of „instructor apprenticeship“ or assistant instructor….
All depends on the teacher, lineage and affiliation ….

Yea I assume that's for coaching purposes but that be only recognized in that specific dojo or gym, I feel like most upper belts should always try to help lower belts to be good comrades anyways but I wouldn't hand out stripes as I had to work for that technical degree so I can teach Profesionaly

I would interpret that as them running their own gym.

I've heard of red bars on colored belts to indicate being an instructor. I've never seen the white edge tabs on any other belt though–again, that's an "I run a gym" marker to me, not just "I teach", but that being said I guess there's not a single formalized standard out there to refer to, just different traditions for us to draw from.