There's two different things to note here.

The legal aspect and the moral aspect.

Legally, the community is completely in the clear since the terms of service for steemit are clear as day: https://steemit.com/tos.html

All proposed Steem blockchain transactions must be confirmed and recorded in the Steem blockchain via the Steem distributed consensus network (a peer-to-peer network), which is not owned, controlled, or operated by us. The Steem blockchain is operated by a decentralized network of independent third parties. We have no control over the Steem blockchain and therefore cannot and will not ensure that any transaction details you submit via the Services will be confirmed on the Steem blockchain. You acknowledge and agree that the transaction details you submit via the Services may not be completed, or may be substantially delayed, by the Steem blockchain. You may use the Services to submit these details to the Steem blockchain.

If Ned misrepresented Steemit to Tron or provided any guarantees to the contrary, that is between them.

The moral aspect should be covered by the material gathered already and various statements of Ned made over the years. It does not have to be "legally-binding" as there is no legal issue here. It just has to show that the witnesses did not behave immorally.

That being said, I think the soft fork was a rash/rushed decision that should not have occured.