Cool implementation. Great job.
I would favor keeping text only data in the blockchain with the current economics and the infrastructure requirements, though :)
Regarding the app
field in post JSON, there is a convention with the current app ecosystem it should be used with a version attached to the string. (Ex: stfu-app/0.0.1
).
oh, thank you for the hint! I created an issue: https://github.com/pcsg/steemToFileUpload/issues/1 so I will not forget it ;-)