So, it seems like this is a common problem from reading threads here like this one:

and l even posted the first time I installed my Toto. Well, 3 weeks ago I took it out to install a new bathroom floor. When I re-installed it (using a new tank to bowl gasket) I again went through the process of trying to tighten the tank down enough to the bowl to make contact with the three contact points. I made sure to go back and forth tightening each one just a little at a time to keep the pressure even side-to-side. As it got tighter and tighter, and closer to the points, I was getting very worried about how much pressure I was using. Then -- CRACK! -- a noise, that is. I thought for sure I had cracked the tank. But I cannot find a crack, and there has been water in the tank now for three weeks, no leak or moistness on the outside of the tank.

My question is, has anybody else ever heard a noise like this and not cracked the tank? Should I be worried there is some hairline crack I can't see and one of these days I'm going to have a major disaster? Or should I just stop worrying about it?