In Chrome, when you're viewing any page you can use CTRL+U to cause a tab showing the page source for that page to open up.
In looking at this page, for instance, I'll use one of the copies of my own post signature as an example. Here's the HTML code for it:
HTML:
<aside class="message-signature">
<div class="bbWrapper"><span style="font-size: 18px"><span style="color: rgb(85, 57, 130);"><span style="font-family: 'georgia'"><i>Brian </i></span></span></span><span style="font-size: 12px"><span style="color: rgb(0, 0, 0);"><span style="font-family: 'georgia'">- Windows 10 Home, 64-Bit, Version 1903, Build 18362</span></span></span><br />
<span style="font-family: 'trebuchet ms'"><i><span style="font-size: 15px"> <b>A great many people think they are thinking when they are merely rearranging their prejudices.</b></span></i></span><br />
~ William James</div>
</aside>
Notice in this case that the font family is named for the various bits. Now, this is not always the case if something is controlled via a cascading style sheet (CSS) but sometimes it is. If one of the words, or phrases, that's showing up in the odd font is pretty distinctive, do a search for it on the page showing the source to see if a font family is identified. See if two things showing up incorrectly are using the same font family, which would give you a pointer to which font may be corrupted or absent on your machine.
View: https://imgur.com/ZwUhOOk
Since tumblr doesn't really work, I tried with another website but can't find a font-family
View: https://imgur.com/ckfE4Gc
View: https://imgur.com/mNvMYJD
Anyway, by going back on the website and renaming the 'highlighter' class (which looks like has the source of my problems) to a random name it made the weird font dissapear. Soo, I went back to the top of the page, searched for the stylesheet links, opened one and found the highlighter but didn't find any font-family
View: https://imgur.com/9454fO3
I got on the main page, got to the css file and decided there was a problem with the 'bold' font-weight, deleted it and yeah, here was the problem.
View: https://imgur.com/yK7Ft5U
Went back to the source file, ctrl+f font-family and got 36 results, all showing to 'Source Sans Pro', 'Lato', 'Montserrat', 'Helvetica Neue' (which was the font used for .package-extra, .tooltip, .popover and body), 'sans-serif,Verdana,Tahoma', 'monospace', 'inherit', 'Menlo, Monaco, Consolas, "Courier New", monospace'. Now, many of these don't matter but since i found that helvetica was the font with problems i searched for the 3 classes.
View: https://imgur.com/DP3buQ5
View: https://imgur.com/pLN9b7N
Now, looking that these match with the font 'Helvetica' and the problem, thought I may have another look at the font list, and here you go, the parts where the font should be 'BOLD' use the broken helvetica 'BOLD' font.
View: https://imgur.com/fd7A8N4
There are only these 3 variants of the font that have problems, the 2 bolds and one regular. Checked the Arial font too just to be sure. Decided to uninstall, again, these 3 variants and even their name tell what kind of font that is 'bold-OUTLINE'
View: https://imgur.com/pzEsbJz
After uninstalling the first bold, the other 2 fonts dissapeared. Well, they actually didn't just simply dissapear, they transformed back to.. normal?
View: https://imgur.com/edHvJhz
So got back on chrome, deleted cache and reloaded the page..... it is still broken.
Also, checked if Firefox is giving me the same problem. Nope. Firefox is fine. Just fine.
View: https://imgur.com/w8oPUio