Nah, it's sort of carryover from old days of plaintext e-mails, except we still communicate with plaintext a lot, so it's still relevant. It originates from the same space that gave you ALL CAPS = SHOUTING and emoticons.
Typical emphasis characters are underscore and asterisks. Many software will recognize them. Like Markdown parsers. Or like HN, wich italicizes text between asterisks. Or Skype, which responds both to asterisks, underscores, and then probably some more.
Complaining about this is kind of like complaining about using punctuation in an English sentence. It's not the users who are the problem - it's the other crowd, that doesn't know the rules and traditions of the medium.
On a _terminal_ you can't - or couldn't compose characters, so you add a hint in the front and the end of the word.
Just deal with it.
It's like the characters added for simulated deletion, that jokingly tell other suckers^H^H^H^H^H^H^H people what you really think. On a suitably incompatible terminal (or vastly overrated editor), this was actually what it looked like when trying to delete text by pressing backspace or some obscure control-character.
Ahh, and simulated hangup noise that you get when you are criticising Hacker New, although that have never happ485734095-.sdf834-...####+3+323803040830
No, it's not but it's funny that you were so sure it was that you put it as a rhetorical question with a nonsense rant about standards.
It works in Slack and other chat apps, too.
I really enjoyed this talk from Apple's conference this year—it gives a great overview of the sort of conceptual framework a designer has when making specific choices:
https://developer.apple.com/videos/play/wwdc2017/802/