According to the maker, the HTPLA ends up having a Heat Deflection Temperature of over 125°C/250°F, which puts it well over the temperature that you'll find in a dishwasher. Of course, if you're planning to make a piece that will be washed in a dishwasher or even in the sink in order to remove food residue, you're going to want to take the time to sand down the food-facing surface a bit before you boil it to heat treat it. You want to minimize the amount of nooks and crannies that food can hide in or no amount of washing is going to help you out. This also means that you should probably pay very close attention to your design and make sure that there are a few sharp corners and crevices unless they are absolutely required for, say, a mold or a press-print.

If you're talking about the calibration cubes, the boiled one actually does seem a little bit smoother in the hand. It's not a lot, in fact it's barely noticeable, but it's a lot more visually striking because it's less translucent than the unprocessed one. I deliberately chose an angle at which both would be backlit so that the difference would be fairly stark. Boiling definitely seems to cause the crystals to grow larger and thus the material more cloudy.