There is 1 Confirmation popup when you are about to feed a 3* or 4* hero to another and actually 2 Confirmation Popups when you are about to Feed a 5* hero to another.
I don’t believe Support will do anything, since this might actually be recorded into her Activities Log too.
@zephyr1 is correct. Any time a hero comes along you intend to keep, use the Lock Icon as soon as you get him/her/it, even if you plan on having him/her/it sitting on the bench at 1^1 for the time being. Placing them on teams is not a good idea in the long run, because you will run out of team space before you run out of hero cap space.