Watching people use remarkup, quite often (this is especially true for non-engineers), they will just copy-paste an entire link vs the shorthand version which not only looks more compact and less visually distracting, but also doesn't open in a new tab when clicked, and more importantly displays the very useful hovercards as well strike-though visual hint.

Using the shorthand version for links also requires an effort vs plain copy pasting from another tab (especially for wiki links which requires entering the exact relative URL or things don't work.

Enter this:

https://secure.phabricator.com/w/guides/arcanist_workflows/
[[ https://secure.phabricator.com/w/guides/arcanist_workflows/ ]]

should turn into

[[ guides/arcanist_workflows/ ]]

Note that if you try to do the shortlink yourself, you also have the risk of cutting at the wrong place:

[[ /guides/arcanist_workflows/ ]]

which wouldn't work.

You could imagine other automated conversions like

https://secure.phabricator.com/T3510

to

T3510

etc...