SwingsitlikeHogan
Major Champion
Gonna be paranoid now as I tee up or place my ball under conditions of relief. ?. Or get a pen with ink that dries quicker. Interesting.In a nutshell, marking your ball for identification and alignment is fine, no issue. But marking your ball with the intent to gain information on your clubface that you subsequently use in the round is a breach (I have RB confirmation of this, I didn't invent my original answer in this thread). If you are intentionally placing the marked ball on the tee so a mark transfers to your club then you are in breach of 4.3. And repeatedly having that happen "accidentally" does not pass the sniff test - integrity requires you to ensure you are not enabling the mark to be transferred.
Often noticed a mark after hitting an iron. Only understood what it meant for me once my coach had me looking carefully at where on the clubface I was striking the ball as part of my practice work. Then only just realised that that might ‘mean’ something under the rules.