If this is accepted, would like the function to be generalized and added to BLI_string.h.

I don't have a strong opinion on the patch, it can be hard to tell how many faces you have at a glance when you get over 100,000 - 1 milllion.

I think this is useful, it's difficult to see now if you have 1 million or 10 million faces now.

It could be done in number buttons too but doing it only here is already an improvement. In number buttons you usually don't have to type such bigger numbers, if you do it's likely bad UI design or a case where units would help, so I wouldn't worry about that case.

@Bastien Montagne (mont29) thanks for re-assigning, I wasn't sure what to put there :P

stats_format() could be moved to BLI_string. However, one issue is that it's using locale.h to get the locale's separator, maybe it should use blender's methods (iface, etc.)?

About number buttons, the only big numbers I can see are the particles count and the blackbody node. Not sure it's worth it.

the separator could simply be passed as an argument.

Though not sure how important it is to support, and by the looks of it only ascii separators are supported anyway. so it could just be hard coded to use ,.

We don't use locale for number display either.

I believe this is a good change. It makes things more readable and is particularly relevant in the INFO bar as those are all report numbers, not necessarily settings.

I like this! +1. I can't speak for how it is implemented in the patch, but adding commas makes large numbers easier to read. It would be nice if this would carry over to make it more global, but that might be too much work for now.

Alternative suggestion here.
What if we just start abbreviating "million" to the end if the number goes above 999,999.
Eg: instead of "10,528,000" it would show "10.5 million".
That might be even more easily recognizable at a glance.

Though that would add the issue of "what if you actually want to know exactly how many are there".
Food for thought.

@David Michael Sisco (dsisco11) The issue with "10.5 million" is that any change below 100,000 would go unnoticed, and that's a lot of faces/verts.

New patch! with stats_format moved to BLI_string. The separator is now hardcoded with a reminder to fix it in the future.

Rebased so it applies again.
(Should I post this in differential instead?)

Yep, would be good to make a differential, otherwise its hard to give feedback.

Added Diff D646

I'm not sure if this is the right place for discussion (especially as this is closed), but some places are still missing the separator, e.g. the face count in the decimate modifier:

Any plans to add the separators there too?