So when you are holding the other teams flag, you receive no other messages in the place where you normally do. So, why not make it that way?
So here are my suggestions:
#1: in the place where it says you are holding the flag, briefly flash to the other message(such as flag return, assist kill, or kill.
#2: in the place where it says you are holding the flag, put the message above the holding flag message
#3: for assists and flag returns, send the message in chat.
Thanks for reading, and please leave feedback!