Plain text environments never encounter the problem that this symbol solves, which is to reveal that an anchor tag (which is not plain text, and typically has visible text that isn't the URL) leads to some other authority.

But for a text mode interface that does have full blown anchor tags -- not very mainstream -- you have a point.

Reddit is mainstream. Other forums with linking might find the symbol handy.. Not sure why unicode has got to be about SMS..

In Reddit, you [link via Markdown](https://en.wikipedia.org/wiki/Markdown). The site renders this its own way, so it can add a "external link" character if needed - and that character is a part of the user interface; a side channel, not a main signal. E.g. copying from a Reddit post, you wouldn't want to find that character in the pasted text.

There's text-based webbrowsers like Lynx too