Just to be clear, PRE and P are "block" tags so if I use

<pre>line1\nli</pre><pre>ne2\nline3</pre>
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or

<p>line1\nli</p><p>ne2\nline3</p>
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(where \n is a real newline), the middle close+open don't just disappear:

line1
li

ne2
line3

I see two blocks with a blank line between them.

CODE tags where there is a newline in the code become a block. CODE tags that contain no newlines do not become a block. So a close+open is invisible if there are no newlines in either chunk of code. A close+open cannot become invisible for a block unless we special-case it. That would surprise people who expect them to work like other block tags.

                - tye