Unless the toilet is used repeatedly so the incoming water to the tank gets cold enough to cause condensation, it won't cause problems with the tank touching. Most newer toilets do not evacuate all of the water in the tank, so often, it is room temp, then add some cold, it may not get below the dew point and condense as they mix. The outlet of the toilet is smaller than the opening in the toilet flange, so you can safely get at least 1/4" or so while still having the toilet's outlet pointing down the flange and still be able to anchor the bolts. It becomes a major problem if it isn't, though. You also must ensure you get a good wax seal, and shifting it too far will potentially prevent that from happening, so moderation is the key.