Gmail still shows unread messages in bold on the same PC in Firefox and Opera, as well as on an iPhone, so it appears to be Pale Moon-specific, even though the problem appeared on reboot of the latest Win10 update.
Any suggestions appreciated, thank you!
Operating system: Win10 Version 10.0.19043 Build 19043
Browser version: 188.8.131.52
32-bit or 64-bit browser?: 64
Problem URL: https://mail.google.com/mail
Browser theme (if not default): Default I think
Installed plugins: (about:plugins): VLC, Microsoft Office 2010, NPLastPass, Skype Meetings App, Skype for Business Web App
If possible, please include the output of help->troubleshooting information (as text):