I think two separate things are being conflated here.
Nodules usually form at entry sites but I suppose could anywhere, especially with the sphere based fillers. In my case, any I had from
PMMA resolved themselves over time to the point where I couldn't find them any more. With
HA, never really got any or anything that lasted beyond the entry sites fully healing. And I have been jabbed many, many, many times lol.
The fibrosis most refer to tends to also form with the sphere based collagen fillers. My understanding is it almost like every time that collagen implant is disturbed/run through with a cannula it causes it.
PMMA also forms sort of adhesions in a sense that grab onto your tissue. It's why it integrates. My initial
HA fills were more uncomfortable due to him having to work through and around it all. Now that I have so much
HA in a more even layer, the fills have gotten easier (and with less bruising etc after). Last time was very very minimal. I'm curious what next time will be like.
So in my instance, I'd say
HA doesn't really seem to cause either nodules or fibrosis.