The answer is very simple – if you know you have broken a rule, you are required to take the appropriate penalty.
There is no rule in the rule book that explicitly states that this is the case, but the generally accepted policy amongst Juries is that under Rule 2, “sportsmanship”, if you know you have broken a rule and fail to take the appropriate penalty, then you have broken the sportsmanship rule, and the penalty for breaking this rule is a DNE – Disqualification that cannot be dropped from your series score.
During the European summer I sat on a number of hearings with International Juries. Two of them were the RC protesting a competitor for touching a start mark. Once it was proven that the competitor was aware that they had touched the mark, there was almost no discussion – they were given a DNE for the race, and not just a DSQ.
So the message is – if you know you have broken a rule, do your penalty even if you don’t hear a call of “protest” and do not run the risk of a DNE from a protest committee.