Even using {code}. It works, then it doesn't.
Tried pre-formatted, 
paragraph and block quotes, and finally {code}. The latter appears to work despite being unable to select the code snippet and encapsulate. Worse still, on further editing the code formatting is lost and the mess reappears.
This has been a source of daily frustration for years.
Note that even this community page is incapable of formatting this editing box with the uploaded attachments. Then when I attempt to "Publish" the question using the button below, a warning tells me I will lose unsaved changes and asks if I want to leave.

Not to mention losing text, the cursor jumping around, and other unpredictable and frustrating behaviour.