Thank you for the comments. A few clarifications are necessary, I believe: If you are referring to item 5 in the first list ("Ctrl-C, Ctrl-V"), it does not copy the text into a plain text location, it clipboards the fragment and then immediately pastes it over itself---in place. Thus, the text stays in the code block but its formatting is destroyed. The description above the list explicitly mentions "pasting text into code blocks". When I'm selecting several lines in a code block then do Ctrl-C, Ctrl-V, all newlines are preserved just fine except the last one. So clearly, Evernote does know how to process newlines in general---it just has issues with the trailing newline. Also, I've just noticed that code block formatting is destroyed when I Ctrl-C, Ctrl-V a single line or its fragment, but not when copypasting several lines from the Evernote client (it's still destroyed when pasting 2+ lines from Notepad). Go figure. Except that it's also buggy: it inserts an extra newline then (and destroys formatting).
[Disclaimer: I have tried to find a proper way to report bugs and failed. "Help & Learning / Submit a request" tells me to "Please submit a ticket" but doesn't say how.] Greetings. Copying and pasting in code blocks has been flaky as far as can I remember, but after I updated from 6.4 to 6.6 it has become almost unusable due to formatting being destroyed. I was unable to find a way to paste text into code blocks while preserving the font. Make a new note. Click "Code Block". Type "abc abc abc". Select any fragment of that line. Ctrl-C, Ctrl-V. In Evernote for windows: observe how the font has changed. In the browser-based client: not just the font, but also the general line height changes (e.g., if you paste text into the second line of the code block, the first line moves vertically). On a related note, pasting text (into notes in general) contaning newlines is also buggy. In the desktop client: Copying a full line (including EOL) from a note then pasting it back does not insert the newline. Copying a full line (including EOL) from another app (e.g. Notepad) then pasting it into a note inserts a double newline. Pressing Ctrl-Z (Undo) after that moves the cursor to an unrelated location.