Is it possible that developers of themes have intentionally changed the code to simplify the implementation of their theme? Perhaps some themes cause registration conflicts, so they just remove all the registration functions from the background, but forgot to tell us to switch off the “users must be registered” function in admin?
There must be some theme developers on this board who know the answer. If it is just an unintentional glitch, then perhaps we can just insert the standard “comments-pst-id” and “wp-unfiltered-html-comment” files into the new theme?