Kyle Scheuerlein

Automatically turn all posts into excerpts of 300 characters and add a “Show More” link that will load directly in the page. If your post includes a picture, it will also obtain a thumbnail and place that at the beginning of the excerpt. Supports Infinite Scroll, too (assuming you manually enabled it on your P2 site)!
<ul>
<li>Shorter posts will be left alone, unless they have a picture</li>
<li>Posts with a picture will always be turned into a thumbnail/excerpt</li>
<li>Expanding or contracting a post will scroll to the top of the post</li>
</ul>
Planned:
<ul>
<li>Long posts with embedded video and no image include the video in the excerpt</li>
<li>Change the character length from the admin screen</li>
</ul>

Show More for P2

Works smoothly even on latest WordPress & Mercury child theme of P2.

Plug and play

Automatically turn all posts into excerpts of 300 characters and add a "Show More" link that will load directly in the page.

Thorsten Ott

Simple widget to extend P2s (and other themes) functionality and display recent @replies for a logged in user in the sidebar. 
It can be also configured to show direct replies to comments or posts without the @username indication.

Mention-Me Widget

11-year old plugin and it still works just fine! Sweet!

It works!

Simple widget to extend P2s (and other themes) functionality and display recent @replies for a logged in user in the sidebar.

Show More for P2 vs Mention-Me Widget