Spaces are always inserted in the most annoying places
Auto insert of spaces feature is a bug, or at least an anti-feature, because it never helps, and often ruins usernames and emails containing punctuation and leaves trailing spaces when tapping a prediction on the last word. I swear every two minutes I have to go back and make careful corrections because of random spaces added by swiftkey. Kill the auto space, kill it with fire!
I run over the space bar at the most inconvenient times. My problem perhaps but ...
Graham Poulter commented
Well, easiest workaround is just to switch to standard Android keyboard for user and password entry