Confirmed, kindling that were player made never stacked.
But there is a stack problem that needs to be fixed, I have yet to see a list over items.
Right now im having problems with:
Muculent
Gobling blood
Seared fire ant goo
peculiar seeds
and thats why I actually went to this forum at this point.
With the last item, peculiar seeds, if you have not identified them with poppies dust, please be aware that there are at least 17 different varieties and only seeds that are the same type will stack with each other. This means you could be hunting for a long time before you will start to see stacks of peculiar seeds form in your backpack or container.
If you have old seeds from before the patch that made seeds stack, please take them to the Gardener's Toolbox located in the garden behind the Palace in Nujel'm (sextant coordinates 27o 31'N, 163o 41'E) and either drop them in one at a time, or in a container if they are already in a container. The Gardener's Toolbox will stack your seeds and automatically return them to wherever the container was dragged from, so if you use a pack animal to transport the seeds, the container used will reappear where you dragged it from in the pack animal.
Now that stacks of seeds can be identifed all at once it makes better sense to simply collect whole stacks of seeds until you have a large amount of them stacked up, and then just identify the whole stack at once thus saving on charges from poppies dust.