If I may be so bold as to make a suggestion. I think this addon would be much much more useful if it had the option to show the summaries of the latest message instead of always showing summary of the first post.
In other words:
1) Write new message "hello world!"
2) Summary now shows "hello world!"
3) Write reply "well hello to yourself"
4) Summary now shows "well hello to yourself"
And people can easily determine from the summary if they are interested in this latest development enough to click on the thread.
I'm not saying "replace the how this works" I'm just saying add the option to select from the config whether it:
A. Shows the summary of the first post (like it does now) or
B. shows the summary of the latest post in the thread.
Thanks for reading my feedback!