I don't want to get out of place, but what I miss very much is that you
'deciding developers' don't decide a general strategy on DEPM and DESM for
the long run. It seems very inconsistent to me to forbid 'enter' formatting
but not 'C-enter' formatting, for instance.
This particular one isn't that inconsistent: Enter terminates a paragraph and starts a new one. Empty paragraphs are disallowed because latex won't print them anyway. Allowing such breaks will merely fool users who don't know latex. This looks like a line break only because paragraphs tend to start on the beginning of the line.
Note that the gap between paragraphs is a rubber length (it stretches an shrinks as necessary) so it is not necessarily a multiple of the line height.If you need more space between paragraphs, use layout-paragraph and specify some length.
ctrl+enter inserts a linebreak without breaking up the paragraph. You can have as many as you like of these, it might be useful if filling out a form perhaps. These breaks have exact line height.
Helge Hafting
