Selecting adjacent blocks of a nestable block and changing type can cause weird behaviours example:

[mitermayer]

Toggling block type to H1

<SELECTION_START><p>asd</p>
<bloquote>
<ul><SELECTION_END>
   <li>
      foo<CURSOR_IS_HERE />
   </li>
</u>
</bloquote>

Expected bahaviour:

<h1>asd</h1>
<bloquote>
<ul>
   <li>
      foo<CURSOR_IS_HERE />
   </li>
</u>
</bloquote>

Whats happening:

<h1>asd</h1>
<h1>
<ul>
   <li>
      foo<CURSOR_IS_HERE />
   </li>
</u>
</h1>

An invalid nesting is created