Everything about a bug report -- including its summary, description, tags, statuses, duplicity, privacy, security, subscribers, and comments -- should be modifiable without going to a separate page. Having separate pages for many of these tasks needlessly takes a lot of developer time. The clutter of form controls can be avoided by making the controls appear only when the relevant information (or an adjacent "Edit" or similar link) is clicked.
This would encompass bug 1328 (Can't add a comment while editing title/description/confidentiality), bug 6457 (Subscribe should work in one click), and bug 28574 (+editstatus and +edit should be one page), and bug 127138 (edit tags).
The first step to implementing this is bug 88172.
As of Feb 2008, it is possible to add a comment from this form.
In progress, but by a whole bunch of developers, not me :)