This is yet another extremely frustrating forum bug. If you're in the process of composing a reply to a comment and the comment is edited, your reply is deleted. This can be extremely annoying if you were composing a long reply.
*Sometimes* your reply will be saved by the forum's auto-save mechanism (so if you press Reply again, the contents will be there). Other times, it won't be.
Bug report:
forums.garmin.com/.../forum-bug-in-progress-reply-is-deleted-if-parent-is-edited