The attached zip file contains to simple SVG files produced with Inkscape 0.46 under Windows 2000.
The first contains just a text object whose content is "half-width space". The space is a regular space. I'm trying to simulate a half-width space by reformatting that space between the two words, giving it half its size (48px before, 24 after).
When I try to this in the obvious way, something strange happens. I select the space with the text tool and use the drop-down to enter the new size. The space then disappears, and if I go to the end of the text with the "End" key, I see a space has been added to the end of the text. (This space is size 48, not 24.)
The XML structure looks even more strange after this action, as the "s" of "space" has been put into a tspan tag of its own. This is shown in the second SVG, produced by saving the file just after the action described above.
Confirmed on Win XP 0.47-pre1. I see the separate tspan's too. I tried to change the size of the space (any value will do) and the space sometimes disappears, sometimes gets displaced two or three chars to the right.