Correction to myself, something strange is definitely happening.
After trying it myself, in my test I have seen the following:
When FTd myself. Running trough fire immediately made me take damage. However, if I did not move and stand in the middle of the fire I did not receive additional damage from the ground, instead my fire status was reduced by 10… while standing in the fire. I was able to stand in the fire while reducing burning status and stop burning altogether, while inside the fire.
Also yes, I can confirm that, while I have seen enemies get hurt while running in trough fire and get a burning status, I have also seen them running safely trough it. With no effect whatsoever.
I also have seen fire status get reduced twice in the same turn.
The only thing I can say, is that fire is completely broken at the moment and is totally inconsistent.
I think this should not be happening at all.