HIGH: [Comment linking] Update thread headers / ancestry to deep link back to the original comment

[quinthar]

Problem:

When you click into a thread, the header says:

• First line: (the comment that is being threaded)
• Second line: From (the room containing the comment being threaded)

When you click the second line, it does open the parent room. However, it scrolls to the bottom of that room, losing context.

Solution:

Now that we have comment linking, when you click the second line, deep link directly to the comment that this thread is under.