The U.S. Congress observes Robert's Rules Of Order, which state that no one within the assembly may interrupt the speaker who currently has the floor. Any comments must be directed to the Chairperson, not the speaker and must be "courteous". Thus, the furor over Rep. Wilson's recent outburst toward President Obama.
That being said, it is, also, a violation of Robert's for members of the assembly to rise while someone else has the floor. However, rising to applaud is done routinely, perhaps because they don't consider a speech from the President to be part of their standard legislative procedure.
