As reported in another thread, spacebar was inserting two spaces in the SDL2 backend, because the event was getting processed twice -- once by the textinput event and once by the keydown event. The one-line fix, attached, is to ignore space within the keydown event.
Edit: ugh, posted in totally the wrong forum. Maybe a mod can move it? It doesn't look like non-mods have the power to delete their own posts...
Many thanks. Added to trunk by prissi in r6876