I know this but I don't want to really want to do this. I think it lowers the quality of the tournament as a whole.
So you think that lowers the quality of the tournament, but you're upset that someone reminded a player of a stupid mistake?
I honestly think its a bit shady of someone not to personally remind an opponent of trample damage.
There's a difference in not advising your opponent on how they tap their lands and telling the opponent they missed something that very clearly would have happened outside of a slip of the mind. The instances in which its better to assign all the trample damage to the creature rather than the opponent are so few and far between its just polite to clarify that they are assigning it all to your creature.
Even if the amount you took that turn wouldn't have changed since the opponent announced damage, a polite reminder doesn't really affect the game.
Edit: and as far as the actual event. I was as confused as Grifter regarding the blocking, but I think the rest of the post sums up my feelings on the actual event pretty well. (as for the blocking...blocking the trample seems to prevent taking future damage when you only have the 3/3 left after the interaction. May not have been a bad call not knowing the rest of the game details. Based on what was said only I would have assumed the opponent would have let Rhino through and saying "take 4" would have been a real possibility based solely on that expectation. Dumb mistakes happen.)
Why would I remind my opponent of trample damage when it is his job to assign it. It's like reminding your opponent that he could play a land for the turn, or cast a spell. If my opponent doesn't know the rules of the game it's not my job to teach him. I think the people calling my play shady are people who don't understand the rules, quite frankly. You are allowed to assign trample damage the way you want.
I was playing for top-8. Next time you're a tournament, practice what you preach and give your opponent strategical advice during the game. After the game, I'm glad to talk about decks and game play decisions. During the game, I'm not going to give them any help. I didn't try to scum the guy, he's the one that said "take 4". I don't know why, but ignorant people keep thinking I'm an angle shooter for doing what I did.
I really don't think you understand how Competitive REL events work. It's fine that you want to have an opinion on the situation but maybe you should familiarize yourself with the tournament scene and environment more before making judgments of people.
I'm with 'Chu on this one, this is an actual real tournament where people are competing. If you're shagging around at FNM or in an otherwise more "for fun" scenario, then yeah I do the reminder thing all the time. But context is a thing and in a real tourney it's your opponent's job to concentrate and play the game well.