yes, that is producing the same result
the space after a /<glyphName> is mainly because you can use both non-glyphName and /<glyphNames> as input:
Su/cool_p er p (if you have a glyph called cool_p)
Copy paste glyph in the input field will try to convert them to unicode characters for display in the input field, that is way the extra space is added.
You could also drag and drop glyph on the input fields.
negative linespacing? the SpaceCenter only gives some basic layout options if you want to test your font with more depth I would recommend to try test install and setup a template in text setting app.
In the waterfall mode only the first line is editable
Any plans to make a "Built Names" button in the Font Info panel to quickly build General, Open Type, and Postscript names? This would be a great time saver and much appreciated.
I just spent a long time getting my interpolated fonts in a family to show up, finally realizing that I hadn't set the postscript name (this didn't seem to matter so much in fontlab), only having set the general and open type names, and this was causing a conflict with the "unique ID" being the same for multiple fonts.
this could be a nice extension
I don't think I will embed it into the app natively, such a feature is similar like drawing with primitives that already exists as an extension (see http://doc.robofont.com/extensions/shapes-tool/ )