Top Sirloin?

the 'bad smoke' when you shut the dome is fat dripping on a dying fire. it does not burn cleanly.

the "swear dwell" method in the BGE cookbook (maybe DVD now) is really only good for something with almost no fat, like a tenderloin. even then, it's not a great way to cook, because the meat sits in a cloud of soot

a candle burns nice and clean until you blow it out. the wick is still burning, but poorly, and that little wisp of sooty smoke is the same thing that's happening in your egg on a larger scale. add to that the dripping fat... and it's a pretty sad environment for a nice steak

quite a few people put it back on after a rest. what is the concern?

with a thick piece of meat you need to divide and conquer. you can cook something thin by searing alone, but anything really thick should be attacked in two stages. sear and roast. doesn't much matter which comes first. and you could even skip the sear

you could hot tub it, to raise the core temp, and then sear to your liking. or you can sear, take it off to rest, drop temps to 400, and put it back on (about a 15 minute wait for temps to come down). or you could roast slowly (anywhere from 250 to 400) until you are within 10-15 degrees of the target internal temp, then jack the temps and sear it to finish.

all these things treat the exterior sear as a small separate step for taste/looks/color etc. the other step more slowly raises the temps internally

no