Is the Visual Bounding box an actual SVG thing? Or is it an Inkscape thing? If an Inkscape thing, theoretically we could just add another bounding box mode... something like Logical Bounding Box.
I checked out both how Draw and AI handle it... and they both handle text and whitespace differently.
Just to note, in both apps you can create empty text frames... Draw uses faux placeholder text though instead of leaving it effectively invisible when unselected.
Now on to "normal" text...
As for leading:
In Draw, you can't even add leading whitespace. It just moves the exiting text object forward by the expected distance... it feels really weird.
In AI, you can add it, it is selectable, it expands their bbox.
As for trailing:
In Draw you can add it, it is not selectable with the selection tool and does not expand their bbox.
In AI, treats it like it does leading.
To me, I think AI's way is just more logical... if you are adding spaces at the beginning or end of text, you are probably intentionally doing it for some reason.
As mentioned in the bug report discussion, if we're going to be nitpicky about the Visual bbox, it's pretty broken when using filters as far as a user is concerned.
Cheers,
Josh