Unable to perform workflow actions, comment on issues, etc

I have been trying out Bitbucket for an open source project of mine (https://bitbucket.org/MattiasBertilsson/com.osisc.eclipse) and wanted to test the built-in issue tracker.

Having successfully created a couple of issues, I am unable to do much with them using the web UI. Trying to comment on them results in a endlessly spinning busy indicator and the operation has to be cancelled. Requesting a preview of a comment results in a dialog: "Error: There was an error rendering your preview.". Trying to perform workflow actions results in an error marker and raw html dump (see reopen.png).

Commenting and performing workflow actions on issues through commit comments works just fine.