When a wiki is renamed (=its database name and/or table prefix is changed) the existing Flow discussions are lost because the wiki ID (given by MediaWiki’s function wfWikiID() is changed.
I propose to create a maintenance script to change the database columns where this reference is written. Probably this script will have two mandatory arguments: the old name and the new name; possibly one can be automatically retrieved if the script is run before or after the rename operation.