The normal procedure for US players who have had caps with the US Men's National Team when they want to come back into MLS is to force them through the 'Allocation Process', a procedure meant to spread USMNT caliber talent all over the league. Kamani Hill fit that bill, though with two caps to his name. No real fuss was made about the allocation process after the signing was made and it wasn't mentioned at all in most reports.
Our friend Steven Goff (@Soccerinsider on twitter) tweeted shortly after the signing that Hill did indeed go through allocation to get to the Rapids.
Kamani Hill did go through
#MLS allocation process. Rapids were only team to enter.
So the reason we probably didn't hear much of anything about it is because nobody was interested except for Colorado, unlike when Eddie Johnson came back and a big deal was made because there were several teams rumored to be interested. It's probably not going to be a concern for the Rapids in the near future since under their new system they don't seem to be in the mood to sign any Charlie Davies style high profile Americans.
Hill was probably signed because he didn't take up an international slot and showed well enough in his trial period to let them know he would be solid depth. They seem to be using the international slots on guys they know will be starting like Martin Rivero, Luis Zapata and Jaime Castrillon.