I try these days to use Mode 1 (freq change only) so I only reply when ready (more realistic after all!), but I notice that although most replies only go out to ATC when I click the right key, a few are spoken anyway, even in the mode 1. The first is the clearance acknowledgement (but that doesn't really matter). However, when I am given a runway for landing, the 'pilot' replies automatically, accepting the runway. I'd rather, like most other commands in this mode, that the response is only given when I am ready - as sometimes I want to change runway. Doing that after I have accepted the one originally assigned every time seems a bit 'daft'.
Why does this reply come automatically when the others wait for user input? Possible to change that?