When using the wiki markup editor in JIRA it's possible to accidentally lose any changes you've made to the content. In my case, it meant losing a few hundred words that I'd written up for an issue and then went back to apply formatting.

Steps to reproduce.

1. Begin editing the description of an issue.
2. Make some changes (e.g. add some text) but don't commit the changes yet.
3. Click the "Style" button, to reveal the different paragraph styles .
4. Press ESC to dismiss the popup.

Doing this will dismiss the popup and the editor. This means you will lose your changes. This is incredibly annoying when it happens.