Did this update get tested across all browsers?
In Chrome, the main page of each forum is an unreadable mass of bold text in similar font sizes: http://screencast.com/t/SaCOb8pfQ Ow--my eyes!
In Safari, it's much more readable: http://screencast.com/t/QPIZyRFn49T
It also looks good in firefox: http://screencast.com/t/SSXdDal0R
Although in both, it makes no sense to have the "Started by" text in a font size that's so similar to the thread title.
The only difference there is in the threads you've read.
If a thread is unread, it's bold.
If a thread is read, it is not bold.
Perhaps I am confused about what you're upset about?