What is the difference between “Refresh” (F5) and “Refresh All Maps” (F6) on the Comment Mapping screen?

Refresh (F5) is actually “Refresh Filter”. It refreshes the “Unmapped” filter. Refresh All Maps (F6) clears the maps from memory so that they are loaded fresh the next time a comment is accessed. “Refresh All Maps” would be used when more than one user is working on a set of comments to make sure you have the latest version.