Reading up it seems that doing python -i will start the python interpreter (these are the >>>> symbols you see), so you are right, it's not the same as just doing evennia.py start, it's just the wrong call since you are not passing any argument to evennia.py but to python directly. So either way it's definitely not the same as starting with evennia.py -i start (which you can tell from the result - it says the Server logs to a log file rather than to the terminal).
I've never seen this problem before, there are no issues running normally over an ssh connection as far as I know. I've never run the server with python -i either to be honest and that you can get it to work launching it like that but not in the normal way is quite strange indeed. I'm intrigued now. Did you maybe redirect your stdout in your ssh window? Do you have some strange environment variables going? Seeing how it works locally will indeed be most interesting.
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Griatch