Repeatedly softening ice cream in the microwave My wife is in the habit of making ice cream easier to serve up by defrosting it in the microwave for 20 seconds or so to soften it.  After serving, the ice cream goes back in the freezer until the next time. 

I estimate that a 2 litre tub of ice cream may well be microwaved and then re-frozen 6-8 times. 

Is it safe to do this? Is it safer, or less safe, than just letting the ice cream defrost at room temperature for half an hour?
It's perfectly safe to do this, it's not great for the ice cream's consistency to keep warming it and cooling it as you'll start to get big ice crystals. I'd suggest you get a metal ice cream scoop and put it in hot water instead. 

If you have to thaw it to use it I'd leave it on the counter for 10 minutes instead of nuking it so you get an even thaw, using the microwave tends to melt one spot and leave another solid.