Helm Hard Over
The idea is that it shows the other boat is infringing rule 15. The problem is that the rule says the boat aquiring rights has to give "room". This requires the keep clear boat to "manoeuver promptly in a seamanlike way" - that does not mean just pushing the helm away. Too often the mainsheet is left loose - well it would be, as the windward boat often doesn't want to move forward and go over the line, but failure to pull in the mainsheet is not in my opinion "seamanlike". If later rules (RRS42) can talk about "rolling the boat to facilitate steering" I think pulling the sheet in is a a pretty basic seamanlike action.
The hail, far from having the desired effect, often draws the Umpires attention to a situation where, had there been no hail, he would have had to green flag, since he would not be aware of times and distances. With the hail he can clearly see what the windward boat is doing and, if it is not seamanlike there is no problem with giving a penalty.
The other call that annoys is "I'm head to wind". So what! You are still windward boat and if you can tack off that is what you have to do.