If you add a thread in Thread Watcher while in catalog mode, it appears as the comment text or the uploaded image filename (instead of the subject)

[darkred]

• Most threads' first posts have both subject and comment text.
  Such posts, if you click watch while in catalog mode,
  they appear in the Thread Watcher as their comment text, instead of the subject.
  But, If you click to watch such posts while you view the thread
  they appear in the Thread Watcher ok, as their subject.
• Also, a lot of first posts have only subject.
  Such posts, if you click watch while in catalog mode,
  they appear as the filename of the uploaded image, instead of the subject.
  If, instead, you click watch while you view the thread,
  they appear in the Thread Watcher ok, as their subject.
• Lastly, other first posts have only comment text.
  Such posts if you click to watch them in either catalog mode or while viewing the thread,
  they appear in the Thread Watcher ok, as their comment text.

So, adding a thread (with subject+comment text or just subject) in Thread Watcher
while in catalog mode has the above two issues - in both cases the subject should appear.

[desuwa]

tl;dr: subjects weren't taken into account when generating the excerpt.

[darkred]

Thanks for fixing this.