I don't pretend to know all the rules and regulations. Duscussion is fine but if you are going to accuse others of illegal commuting then please back up your claim.
If your friend saw pilots in uniform in the cabin then they were probably regular voluntary commuters. I know many of those and as I already tried to explain above, it is not illegal at all nor is there any tax evasion. It is a standard approved written procedure. If you think it is somehow unfair, then ask your company to adopt those rules that so benefit Ryanair and other European pilots.