I'm not having any font problems in 10.6.8. If you want to try it again and you want to revert to 10.6.3, boot from your SD (10.6.3) clone, erase the 10.6.8 drive, and clone back from 10.6.3 to the (former) 10.6.8 drive.

If you have the same issue after re-updating to 10.6.8, use Font Book to resolve duplicates and disable any questionable fonts. If you start up in Safe Mode, that will run a number of diagnostics, including clearing font caches.

Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365