Changing the label in admin should change the usage of label everywhere on the community. If you change dog to cat, then it will be updated in all existing threads that use it.  Hope this helps. ... View more

You can edit labels in Community Admin>Features>Labels>Edit Labels. Changes made here will update all usage of the label across the community. It can take up to 10 minutes to see all the UI update to reflect this change. This feature is only available at the community level and can not be used to make changes on a specific node only. ... View more