The bug
Blocks which are not flammable cannot support fire on their side faces or bottom faces, despite the fact they can support fire on their top faces.
Linked issues
is duplicated by 3
Attachments
Comments 21
Working as intended, blocks which do not burn from fire will not be lit from there sides, however blocks which can burn such as wood can be lite from there side.

How is this working as intended if we haven't gotten an official statement from Mojang on it? It's kindof an odd situation that it works in some situations (like on the top of the block) and not others (on the side). Would be especially neat if it worked on the sides of netherrack, then you could create a literal wall of constantly-burning fire.
This isn't intented... this is a glitch when I was in the nether I tried to fire the blocks but it glitched and it dont work!
I would like to request ownership, because the reporter has not been active since 2013
This seems to be reporting the opposite of MC-4923 (fire can be placed, but disappears), which got fixed (no more fire placed) (meaning that it cannot create fire there is intended).
Can confirm in 1.18.2 and 22w18a.
Can confirm in 1.19 and 22w24a.
Can confirm in 1.19.2.

Can confirm in 1.21.4.
Confirmed.