@zep, I am finding this line by itself in code:

while a < anything do

while a < anything do

Is not appearing entirely ^^ above in [ code ] if you take out the space before and after the <
This is happening in PREVIEW. Once I post I'll let you know if it appears as a POST too.

This is quite puzzling. I also have my ad-blocker turned off.
Windows 10, Quad processor, Firefox v105.0.1

while a<anything do

while a<anything do

O K A Y it only happens in PREVIEW. Here, create a new message and copy that while a<anything do inside [ code ] and PREVIEW your message before you post. See if you get the same results I do.

This is what I see when I PREVIEW the message:

Please let me know if you ARE or ARE NOT receiving this error on your side.