Is it true that the more times you have covid the less severe the illness?

This would seem a reasonable assumption, but it is not known and no study has reported this. A confounding issue seems to be that mRNA immunizations seem to potentiate getting future infections. A recent scientific consensus seems to be that infection in a non-vaccinated person confers immunity that is several times stronger & possibly more durable than immunity provided by mRNA immunization.

Aside from controversial results of late studies my esteemed colleagues mentioned, COVID is a continuously mutating virus with some strains more contagious or more pathogenic than others, not to mention that individual immunity may be different as individuals may be weak recovering after a different acute condition or fighting chronic conditions/ being on medicine altering their own immunity.