Be so kind to take a look at this page, but look at it in a screen resolution of 1024 x 768 or lower.

Then you will see that the comment form is too wide and that the mainbody text will disappear under the right sidebar.
I thought this would be a sitetemplate issue (Joomlart 'Bellatrix' ), but it seems to be a JoomlaComment problem.

Where do i need to edit the code to make the form adjust automatically to the screensize or give a save fixed width of say ... 800 px?

Kind regards,
Rob