Officially the increased sickness effect doesn't exist at all. We only have these sorts of anecdotes and vaccines can only be discussed occasionally on HN, and not at all on most other forums, so notes can only be compared rarely.
Unofficially the effect does exist and goes by various names: OAS, Hoskins Effect, immune imprinting. It can be seen in some of the vaccine effectiveness data back when it was being collected by places like the UK, where vaccinated people were getting COVID at 4x the rate of unvaccinated by the time they stopped reporting (and the rate was worsening with time).
It can also be seen in the boosters trial data where they had to switch the definition of success to antibody production, because the boosters were not actually reducing infection incidence e.g. the bivalent boosters were tested on all of 8 mice and all 8 got COVID when exposed so effectiveness is zero, but that didn't stop them being approved on the basis that they caused production of antibodies (to the variant targeted by the OG vaccine, not Omicron).
OAS unfortunately can be caused by any vaccine tech. It's not mRNA specific. The antibodies you produce are for the older extinct variants that the vaccine trained you for, not the current variants. The body doesn't recognize that there's a difference.