Truth be told I have no good answer to that. Obviously it would be best to find a setting that works with older content and the fix the newer posts as those will be fewer. What setting that would be however, and it simply switching the setting would do the trick is unknown.
When the database was exported in order to be moved, it was exported to plain text and some information might have been corrupted at that point, making any setting irrelevant following the import as the data might already have been corrupted.
If you look at some very old threads (around 2008 or so) you can see the same issue, stemming from a similar situation in the past.