Avoid double escaping in Remarkup
Summary:
These all work with plain text.
Fixes T2574.
Test Plan:
> [[ a | <a> ]]
- [[ /a | <a> ]]
//a**b**c//
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2574
Differential Revision: https://secure.phabricator.com/D5060