The steam under a cover is a burn waiting to happen. Chicken cooked other ways isn't usually covered, so holding steam around chicken isn't a necessary part of cooking it, and I'm not trying to steam it like it was veggies, so... other than preventing splatters, is there any actual NEED to cover chicken, whether with a lid, Saran wrap, wax paper or anything else, while cooking it in the microwave?
The primary reason you cover any food in the microwave is to prevent spatters and reduce your amount of cleanup.
However, there are secondary reasons, all of which potentially apply to all foods including chicken:
- To retain moisture in the cooked food
- To heat more evenly
- Even to kill bacteria
The last two deserve more explanation. First, you may have noticed that microwaves heat food somewhat unevenly. This is because they have hotspots, only penetrate 2cm or so, and because microwaves heat only the water and fat in the food, not other elements. This means you rely on secondary heating -- radiation and convection from one part of the food to the other -- in order to heat the entire dish. By covering the dish as you heat it, you improve convection heating by trapping the moist heat in a smaller area.
The last reason is particularly applicable to chicken, which often carries salmonella bacteria. When you microwave chicken uncovered, you can end up with cold spots that are barely heated at all, and might still harbor living bacteria. By covering the chicken, you trap steam that will kill surface bacteria by making sure that all of the chicken surface is sufficiently heated (more on salmonella and microwaves here).
BTW, to reduce burn risk: use a microwave dish cover that has small vents, and simply wait 30s or so before taking the food out.