What means standby?
It means wait
The stand-by option is already available to the pilots and ATC
When ATC or a pilot says stand by, it means they are in the middle of something and need to focus on that first. Responding is just another few seconds if unneeded distraction. Lack of a response is the acknowledgement.
I dont reply to standby as well, unless the same aircraft tells me to stand by like 2-3 times, i assume they want an acknowledgement so i reply with a standby.
Though i could do with avoid sending duplicate messages if i feel that person is being quite a terrible person.
Though sometimes IF lags a little and we thought we didn’t tap so we tap again and end up sending duplicate messages unwittingly