No waffle you can kill anybody regardless of chatbox, saber down, or anything.
Some people say "dont kill me, im not playing", no chance, if you let them live, what is to stop them then attacking you from behind, or spam pulling, or interfering in the CTF? Nothing, thats why everybody is a target, playing or not, because i hate it when people say they are not playing, then spam pull or attack you from behind or anything.
Example with queenie last night, she was saber down and claiming she wasnt playing, yet she then kicked me off the ledge to my death when i left her alone. Blackknight was saber down too, yet he kept spam pulling me.
If your in CTF your a target, simple as that, its just tough. So yes, u can lame, typekill or whatever else, dont risk the possibility of leaving them alone, then them getting involved when u are ignoring them.