If there is a passage that thrills you, I see no fault in expressing your joy during the performance, whether you choose to clap or cheer. For the performer, I can see this as nothing less than encouraging.
Rests are important; they give you a chance to digest the music just played and prepare for what's coming
The audience is there to be entertained, not to live in fear of letting a cough or sniffle slip out during a pianissimo passage.