I just added trivial support for cutting exceprts, was a fairly trivial change
<span class='excerpt'>My excerpt here</span>
Allows you to control the excerpt as a mod. Will fix the word truncating as well, surprisingly it is ever so slightly more complicated than this change.
https://github.com/discourse/discourse/commit/de7e6a95459f2e114c89bd1554e3a21861a3ffa7