Since posting analysis in the comments is difficult, I declare this community wiki to be used for sharing our findings!
##Normal tag wiki:
<div class="post-menu">
<form class="form-submit" action="#" method="get">
<input type="button" onclick="window.location.href='/edit-tag-wiki/702'"
value="Edit Tag Wiki">
</form>
<a href="/posts/196614/revisions">history</a>
<span class="lsep">|</span>
<a id="show-wiki-excerpt" href="#">show excerpt</a>
<span class="lsep">|</span>
<a href="/posts/196615/revisions">excerpt history</a>
</div>
##pdf tag wiki:
<div class="post-menu">
<a href="/posts/247236/revisions">history</a>
<span class="lsep">|</span>
<a id="show-wiki-excerpt" href="#">show excerpt</a>
<span class="lsep">|</span>
<a href="/posts/247237/revisions">excerpt history</a>
</div>
The markup for the Edit Tag Wiki button is completely missing and the excerpt history link (https://superuser.com/posts/247237/revisions) is broken.
When examining the latest history source, there is an extra newline at the end of the post (compared to the 'normal' tag wiki above). Could this be causing the bug? Can someone with tag wiki edit privileges try replicating this on a different tag?
