Messages 14.0 crashes when I click on a message from certain senders.

I had the same problem and changing the font worked for me, though my original font was Ariel. Thanks for the suggestion!

I've been having this problem as well whenever there's bold text in a message that I've received. Messages would even crash if I tried pasting problematic text into a message.

The fix for me was to change the font in Messages settings from Geneva to another font. I guess I changed it to Geneva at some point.

Hope this helps.

I'm glad it helped. I was able to view problematic threads from my iPhone and noticed that it was always messages with bolded text. I would always delete that message on my iPhone and then be able to continue using the thread on my Mac. Since others weren't experiencing the same problem, I figured it was something on my end.

Changing the font setting in Messages seemed like a good thing to try and, sure enough, that fixed it. I remember the days when Geneva was the bitmap font for screen viewing and Helvetica was the postscript font for printing, so I must have changed the font to Geneva to make it easier to read onscreen. Probably not many people would have done that, which explains why nobody else seems to be having this problem.