I don't think this can be considered vendor lock-in :) You are probably way more "locked-in" by your language or framework of choice. Plus, you can always download the environment into your local machine and forget about Cloud9 at any time when it doesn't fit your needs anymore.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
I don't think this can be considered vendor lock-in :) You are probably way more "locked-in" by your language or framework of choice. Plus, you can always download the environment into your local machine and forget about Cloud9 at any time when it doesn't fit your needs anymore.