> PS What append when the angle of the curve is too compound / radius?

But seriously this time - it should actually create a surface in these cases, but the surface will be messy and have kind of self-intersecting folds in it.

A surface like that won't be suitable for many other operations on it that involve calculating intersections on the surface, such as booleans or filleting.

It usually can be exported, but of course the result will also be kind of messy but possibly some times that may be ok depending on what you are doing.

So generally those types of things should be avoided, except in a special case where you are only going to export the surface without further operations on it, and you don't mind the messy polygon arrangement either.

- Michael