Did you ever find an answer to this?
Yes. I used those css changes to get rid of the Freshness display altogether until I could see that the Forum Description at the top of each form was corrected. It’s misleading,o when a topic is created 10 years ago and has had only replies since, to show the “last updated” is 10 years with a reply only months ago.
Thanks to IngeT for leading with the way to map out the bad Freshness data. After cruising around the Forum, I don’t see a good answer to this. The only ticket open appears not to be addressed these last five months on this ticket: https://bbpress.trac.wordpress.org/ticket/2414
