Not an issue once on the pan: Linseed oil oxidises quite quickly when exposed to air which is where the heat is coming from and it's certainly exposed to air on a pan, however, the pan is also an excellent heatsink and not flammable. Rags are a combination of even more exposure to oxygen (because the oil soaks into fibres and then has lots of surface area) combined with the rag being flammable, those are very specific circumstances. Bottles of the stuff also don't spontaneously combust in the fridge, they only spoil within a week or so (for culinary use, that is, it's still perfectly fine to season pans with it, and is still food-safe. Just starts to taste like ass quite quickly but that doesn't matter when you burn the stuff anyway)

But yes I should probably have mentioned that I flush my kitchen tissues when working with linseed oil.