"You're about to leave this site" confirmation

[luxaritas]

Specifically, since markdown-it (7a40759) allows for link creation using custom visible text (ie [Click Here](http://example.com)), I'm thinking it would be good to let the user know if they're heading outside of Eterna, or at least warn the user if the visible text looks like a URL, but the link actually points to somewhere else. Open to discussion as far as how far this should go. I'm imagining a simple modal for this.

[guyguy2001]

Why not simply use a format similiar to the current one, where the link opens a new tab? I mean you usually want to keep being in chat when you are given a link from someone that you are chatting with.

[luxaritas]

Well, yes. This is more of a security-esque thing (ie, so someone can't post a malicious link saying that it's something else). I suppose with a link shortener it's a similar thing (I know a few people tend to use goo.gl - though this probably won't be quite so necessary, as I'm planning on turning on the feature in markdown-it/linkify-it that truncates long links like https://github.com/Eternaga...).

I'm kinda thinking that I should just turn off that feature, not sure that it really makes sense in chat (I know Slack and Discord don't have it).