Hi Nick - it can tend to be difficult to remove those after they've already been created. They don't necessarily have to be removed, that one there is not doing any harm for example.

To remove it would involve deleting those faces and constructing a new larger surface in its place.

The main way that you would get a result like that is because of segmentation in your original curves - if your original curve is made up of many different joined segments, usually when you construct a surface from it the segmentation will inherit into the surface structure with one separate surface resulting from each segment in your original curve.

So if you don't want that you can try to eliminate the segmentation in your original curves before doing any construction off of them. One of the easiest ways to eliminate segmentation on a set of joined smooth pieces is to use the Rebuild command on the segmented joined curve, it will build a new single segment out of any fragmented segments that are smooth to each other:
http://moi3d.com/3.0/docs/moi_command_reference10.htm#rebuild

But a little bit of segmentation is normal and not necessarily something you have to worry too much about. Heavy segmentation especially where some of the pieces are really small is not good though.

- Michael