When filling one burner inserter using another burner inserter, the second burner inserter is filled based on fuel value rather than auto inserter limit (the first inserter has a fill limit of 1 fuel which is expected based on their old behavior). This doesn't seem to apply to other fuel powered entities.
Kept failing a speedrun because of this and couldn't figure out why until I realized there was 10,000 more coal in my inserters than I had planned for in my 1.1 design
This is most likely related to 120114 where burner logic was made specifically to not obey the inserter limit if item does not provide energy for at least 3 seconds of machine work. I see where this logic could fail with burner inserters: they get their buffer size relatively large due to initial energy they are given "for free" and so the logic thinks it needs to insert fuel to be at least 0.4MJ (buffer size) * 180 (ticks) = 72MJ.