Chasecam.

Does anybody make demos while in chasecam mode? Just wondering, because that would be sweet to watch.

Engines with a chase cam have it so you can turn it on or off at will; it's just a visual feature and it doesn't affect the demos. You can always watch any demo on chase cam mode if such a feature exists, or watch a demo supposedly recorded with chase cam on from a 1st person perspective.

I'd be surprised if anyone recorded in chasecam mode - this would surely just be a handicap, and it would also restrict your choice of engine.

As myk says, this doesn't stop you watching in chasecam mode. Of the engines that have demo compatibility with the original game (and Boom, etc.), Eternity and the experimental Prboom 2.3.0 have a chasecam feature. Eternity also has a walkcam, as does OnyxStar's modified version of Prboom 2.3.0.

one small addition: the DDQ and D2DQ movies are chasecam demos(or First person if desired).