My 2013 Punto all last winter had fogged up rear light clusters, I find it pretty annoying but from searching online it seems to be very common as the LED lights don't heat up enough to ever clear the lights.
I now find my car after weeks of sunny weather with still some condensation in the offside rear light

I've read people had their lights replaced at the dealer although the issue persisted. Has there ever been a fix for it now its been some 10 years since the Punto were first fitted with this light cluster?

Mine were noticably misty last week..

I dont think there is a 'cure'

But removing and 'drying' could be a sensible experiment..
Folklore says its down to a poor seal against the bodywork..I am not convinced

Its very annoying! I may try and clear the dirt behind them between the light cluster and the body to help them 'vent'. I'm doubtful it'll work, during the winter they can fog up to a point of reducing the output which you'd think Fiat would need to address....

We have a 2013 Punto Sporting Multiair 105. Ultimately condensation corrodes the PCB in the light unit & they fail. Had one fail in 2016 at first MOT (not bright enough). Fiat replaced under warranty but the genuine LED light units are about £120 each to replace - comes as a whole light assembly. Well worth trying to dry out before it gets to that stage if you can.