this seems to be a bug in the template files in 3.4 (and 3.4.1 as well). however, if you change "can_create" into "create" in the right .tpl file in your ez design directory, you can post comments.
for me it worked like this (i wanted to have anonymous weblog comments):
1. edit <ez_dir>/design/<name_of_your_ez_site>/override/templates/full/weblog.tpl
2. look for "can_create" at the bottom of the file, replace with "create"
3. clear template caches in the cache admin 4. make sure the anonymous role has sufficient rights to post comments
