I checked with my colleges on this. In regards to opening new issues we won't allow external creators, since we want to pre-qualify/reproduce these issues before they hit the development teams. Therefore if you have a subscription the best way would be to open a support case to create a Jira ticket. If you use the community edition then posting on the forum is the way to find someone for your cause.

The good news is that we have plans to open up comments for external users. At first only to partners where we know that they will be willing to use beta releases, if that works out this will be expanded to a broader audience. No date is set for that, though.