I am working on clearing my beer, started using Whirlfloc, giving it time, etc in the primary. I read about some allowing beer to clear in a keg, doesn't the keg get clogged with the settlings? If cleared in a keg, what happens when you carbonate, doesn't it just get mixed up again?
I worried about the same thing when I started kegging. Surprisingly, it doesn't clog up the pick up tube. Now of course that's dependent on how much junk there is to settle out. The end of every keg has a layer or yeast/proteins in the base even with the clearest beers.
My beers tend to sit in primary for 14-20 days. They are pretty free of sediment at that point. I go from there directly into kegs. They sit cold and more stuff comes out.
As for carbonation stirring it up, that's only a concern in special cases. First, if the keg is moved it will stir up sediment for sure. If you overcarbonte the beer and need to release pressure using the PRV, I have found a clear beer will cloud up. I think this is because once you release the pressure the sediment nucleates with CO2 and some of the CO2 then lifts the particles up into the beer a bit. It eventually settles back out.
As long as the pressure stays on the beer and the beer isn't mechanically stirred (lifting the keg to carry it around for example) the stuff stays in the bottom. Just like bottle conditioned beer.