I've never heard of "tone indicators" before, but I've seen the usage of "/s" for a long time to indicate sarcasm, possibly as early as the 90s.
Emojis as well, though they were pure ASCII, not the emoticons of today
emojis are technically the UTF-8 style emoticons, so you do have a point that i shouldn't call ascii style emoticons this, but its really a redundant distinction in my opinion. Especially as the term emoticon also applies to emojis/picture representations of ascii-style emoticons.
As far as I know, the term was coined in the 90th. Please take note that i've - from the start, talked about the term, not the usage of punctuation to show faces
https://archive.org/details/ParalanguageInElectronicMail-ACa...