While I playing with the new official feature "Clean Up Bags" I notice that Bagnon has to override "SetSortBagsRightToLeft(true)" (sortButton.lua, line 56) to avoid weird "gap" in the other direction of sorting (I believe you would know what I mean). Would you consider that rearranging the layout(order) of bags is a better and more consistent solution? That is, to match the layout with official UI, let the Backpack be the rightmost and 4th bag be the leftmost one.

I know Bagnon has a "Reverse bag slot ordering" option, which makes the ordering same with official UI, but it's not the default of Bagnon, and I feel that in official Interface Option the description of "rightmost bags" "leftmost bags" is very confusing to Bagnon users.

I personally love Bagnon especially because it's ordering slots in a reasonable way. Blizzard's UI is rather unintuitive. However, I agree that "rightmost" and "leftmost bag" are not all that clear when using Bagnon.
But of course, with Bagnon enabled, one could just swap the label texts ;)

I agree with ckaotik, and I believe the majority users would as well. I will relabel and disable unusable buttons.

ckaotik is right, you had the point I missed when I posted. I figured out it on my own too, it was one of the reasons I switched to Bagnon in the very beginning (wow old days :p).