Yesterday (Aug 26, 2014) Google released Chrome 37 and one of the changes is how fonts are rendered.
If you think TL changed the font, it's because your Chrome finally updated and is using the new DirectWrite font rendering. This is good for large text but if you're someone like me that hates anything new (long live broodwar!!) then you might want to change it back.
How to change it back:
1. Type chrome:flags in your URL bar.
2. Look for Disable DirectWrite Windows and click "Enable"
Thanks! I've disabled this thing, prefer the older style. Much easier to read. Maybe this thread could get a spotlight, many people will be pleased to know there is a fix.