Yesterday I added release with title containing straight quote character " (ASCII 0x22):
7" split
http://musicbrainz.org/release/6af45d95-1edc-4e8a-b6cc-8df5853734d3

Later I noticed that on the title page (http://musicbrainz.org/) in "Recent Additions" the pop-up text showed only "7" instead of the complete title and artist:
7" split by Houpací koně / Please the Trees
In the HTML code we can see that the quote character was probably wrongly escaped and the software even produced nonsensical HTML attributes:

<h2>Recent Additions</h2>
<div style="height: 160px; overflow: hidden;">
<div class="artwork-cont" style="text-align: center">
<div class="artwork">
<a title="7" split="" by="" houpací="" koně="" please="" the="" trees"="" href="http://musicbrainz.org/release/6af45d95-1edc-4e8a-b6cc-8df5853734d3"> <img src="//coverartarchive.org/release/6af45d95-1edc-4e8a-b6cc-8df5853734d3/3627652141-250.jpg">

The part of the HTML code is attached as MB-title-recent_additions.html.

Note: I should have probably used the typographically correct double prime symbol instead of the double straight quote in the title http://en.wikipedia.org/wiki/Prime_%28symbol%29
I will correct the title later.