[bug] Replying to thread causes title with special characters to break

[ponens]

One of the new features I noticed was that when a reply is made to a thread in which the last post is also by the same author, the post is instead appended to the last post. This causes a bug to occur with the thread title however -- if a thread has the special characters "<" or ">", it gets "double-escaped", so somehow the HTML entites "&lt;" and "&gt;" gets translated to "&amp;lt;" and "&amp;gt;", which in turns renders as "&lt;" and "&gt;" on screen. This only occurs if the reply is appended to the opening post (as that is the only post that has a title). (see below) It doesn't actually affect the thread title shown on the thread list; it just affects the "secondary" title that appears in the lightly shaded banner just before the first post.

Steps to reproduce:
1. Create a thread with "<" and/or ">".
2. Reply to the thread using the same account.

Expected:
3. "Secondary" title should not change.

What happens:
3. The characters "<" and ">" in the "secondary" title get mangled in the process.

[Deleted]

Testing post.

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Appending reply to post.

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Issue occurs with all titled posts, not just OPs.