What was the real reason this project was cancelled (=not deployed widely to all wikis). Was it a lack of community consensus for enabling this (probably at least on English Wikipedia)?
Topic on Extension talk:LiquidThreads
The English Wikipedia had no consensus. In addition, the current version (the one being used here) scales poorly.
There was/is consensus for use of LQT in more than one wiki, even if it scales poorly.
I would guess that it was felt that a new extension (Echo) would better achive the foundation's goals.
Maybe voting is difficult in a traditional thread model
That makes no sense, voting is quite possible on internet forums, all of which necessarily have threaded discussion. I do prefer threaded discussion, and threads can be distributed over multiple pages.
They can with traditional wikitext, but they can't with LQT.
Why is voting possible both on forums and with unstructured wikitext talkpages, but not with liquid threads?
I was replying to "threads can be distributed over multiple pages": they can't, with LQT, because you can't transclude LQT threads.