One annoying quirk that I’ve seen:

I’ll start a power down command sequence with a TV Power OFF command. This suppresses annoying messages displayed on the TV as input devices are powered down. Near the end of the command sequence the cable box will assume that I must want to watch cable and the cable box sends a CEC command to Power ON the TV. Initially you might assume that the TV never powered down, but this is not the case. The solution is to send a second Power OFF command to the TV or use CEC suppressors.