On the report content endpoint
we remove the required flag for both the reason and score parameters, as
well as the "may be blank" clause in the description of reason.
Currently, the spec says that the reason parameter on the content reporting
endpoint is required, but also says that the string "may be blank." This
seems to be a contradiction.
Note that the kicking and banning endpoints already have optional reason
parameters. The other membership endpoints mentioned in
#2367 will also add optional reason parameters,
so it would be more more consistent with the rest of the spec to make this
optional as well.
The spec also requires the score parameter, but its usefulness is limited.
Offensiveness is difficult to measure and is likely not going to be applied
consistently across several rooms. Because of this ambiguity, it seems, many
clients simply hard-code the integer value.
To make this useful, for example, room administrators would need a way to map more specific values to the integer range and perhaps even instruct the client to display those mappings to the user. That may be possible to do in a closed client/homeserver implementation, but not generally across the Matrix protocol.
Making score optional would enable this feature to be used in specific contexts
while not forcing clients to support the ambiguity it brings.
Since servers currently expect these fields to be sent by all clients, making them optional is a breaking change. Clients should check the spec versions the homeserver supports to detect this change.