This is how you end up with police making up an “anonymous tip” which allows them to gain a warrant and dig through the personal possessions of anyone they don’t like.
The problem isn’t solve with anonymity, but by actually protecting the whistle blowers.
My gut suggests it’s a font issue, like librewolf is using a system font and firefox is using embedded or downloaded fonts.
backing that up with a search, I see there’s lots of people complaining of font rendering issues of various types in the librewolf subreddit: https://www.reddit.com/r/LibreWolf/search/?q=font
I don’t know what your fix is, but I hope this helps guide you.