I guess you might consider this a feature request:
If you create a new issue in Jira, cancelling or attempting to navigate away from the page before saving will prompt for confirmation. There is no such safeguard in place for comments. Has anyone requested this before, and is it possible to add to your feature backlog? It's pretty frustrating to write in a long comment adding information about an issue only to mis-click and lose all your work from the last 5-15 minutes.