For the moment I stopped using it.
As a temporary solution, I'll need to know which file of AJAX threads to edit and there to add these two lines before code for posting posts:
PHP Code:
$post['replylink'] = true;
$show['multiquote_post'] = true;
This would manually force quote and multi quote buttons in AJAX threads.
But, on further thinking, this also could be a problem. Maybe ideal solution from my perspective would be mod that would check if post is last in a thread after someone press quote button, and if it is, instead executing code for quoting, just execute code for reply (i.e. quickreply).
Even that in some occasions isn't applicable.
It looks like I'll leave it be for the moment.