Users have pointed out that it is very difficult for beginners to comment on questions, see this thread. These users particularly seem to emphasize that it appears Cross Validated has separate policies regarding comment permissions compared to other stackexchange sites, even though this is actually not the case. The problem actually appears to be that it is much more difficult to get reputation on Cross Validated than it is on other stack exchange sites, because people don't vote as much, as can be documented in this thread.
It is extremely frustrating for a generally trusted stackexchange user to not be able to comment on the answers to questions or even be able to ask for clarification on other people's questions. Could this be addressed by giving reputation a bit more generously or perhaps doing something else. Maybe saying something on the sidebar like, "please up-vote all well researched on topic posts even if you don't feel qualified to do so (it is especially important that you up-vote reasonably worthy newcomers, as their participation is greatly inhibited without up-votes)". The point is, we are all able to tell whether a question is well researched, a duplicate, or reasonably on topic. Down-voting is a bit different you should be qualified in the subject at hand, but our users should feel comfortable up-voting anything they think is appropriate.
We really need to do something about the lack of up-voting in our community. This answer to a previous thread really strikingly uses stats to show just how much of problem voting is. Looking at the first 50 posts on the main-page right now, I see 14 net up-votes given with shockingly 1 up-vote being the max given for a single post!
Other things we could post on the sidebar is (note there may be some disagreement on this suggestion) "You should up-vote every question you answer". The reason for this is that you should not be answering bad questions anyways because (1) it prevents the user from deleting the question and hence decluttering the site (note that bad question clutter makes it difficult for users to tell if their question is a duplicate), (2) It can easily be stated in a comment, (3) It encourages users to ask more bad questions (the main reason question askers come here is to get answers not rep).