when you hit enter, it creates a <br />
    if you're inside a link, it closes the link first

when you hit enter
    if the cursor is immediately preceded by a <br /> then a new p is created
    if you were inside some formatting then that is continued in the new p

so if you had:

<h2><strong>hi there[[HIT ENTER TWICE HERE]]</strong></h2>

you would end up with:

<h2><strong>hi there</strong></h2>
<p><strong>the cursor is here now</strong></p>

but if you only hit enter once you would get:

<h2><strong>hi there<br />and keep typing</strong></h2>

and with a link:

<p><a href="ohai.html">here is my link[[HIT ENTER HERE ONCE]]</a></p>

then you would get:

<p><a href="ohai.html">here is my link</a><br />and type here</p>

but if you hit enter twice:

<p>a href="ohai.html">here is my link</a></p>
<p>no formatting here yet</p>