Kind of, it depends. In my experience so far, Reddit blocks Tor nodes about 20% of the times or so. More specifically, it seems to return a 429, probably because someone tried to abuse Reddit from the same node and Reddit banned the IP. In my experience, this is just as likely to happen with the onion site or the www address.

That being said, I only lurk so I don't know if there are any additional restrictions when trying to log in.

Is that the same issue you have or is it something else?