posts and comments suddenly bolded

Just out of the blue, my posts after a certain date are bolded. But when i click on the permalink, it’s fine.

for example on post march 10 this permalink looks fine here but on the main page it’s bolded throughout!

and in a recent post here the post is fine, but comments were all in bold.

and now my sidebar fonts are all bold!

this wasn’t the case a few weeks ago 🙁
please help, i’m lost!