If members want to let us know when their issue has been resolved, we can edit the thread title for them. I don't think there is an option to allow members to edit thread titles, if it were, I'm not sure it would be wise to allow it.
However, how many members will be aware of doing such is another unknown. Most members won't even read the rules.
As far as asking moderators to keep an eye out for issues that appear to be resolved, I wouldn't ask them to do that because it's enough to do what we all do now.