API /answers/{id}/flags/add route has multiple bugs

Question

The API route to flag an answer has a couple of issues. The first of these may or may not be a bug, but the second definitely is.

Firstly, sending a request that's apparently identical to the example request that the API console sends fails. On trying to flag Stack Overflow answer #40769255, the API console sends the following parameters to https://api.stackexchange.com/2.2/answers/40769255/flags/add:

id: 40769255
option_id: 22992
key: my API key
access_token: my write token
preview: true
filter: default
site: stackoverflow

When I send a similar (semantically identical, apart from the lack of filter parameter) request from my Rails web app to https://api.stackexchange.com/2.2/answers/40769255/flags/add:

option_id: 22992
key: my API key
preview: true
access_token: my write token
site: stackoverflow
id: 40769255

I get the following 400 Bad Request:

{"error_id":400,"error_message":"comment","error_name":"bad_parameter"}

I've also tried including a comment parameter. With an empty parameter, this fails with the same error. With a 16-character comment parameter, the request succeeds (for a NAA flag, which doesn't require a comment). Which leads me on to bug #2...

The flag doesn't get created.

As I said, I was trying to flag #40769255 on Stack Overflow. After the successful request, I opened the flag menu on the answer, expecting it to tell me that I have an NAA flag cast. It doesn't.

Neither does my flag history list any flags on that answer.

This is definitely a bug, since the API request should not return a 200 OK unless the flag has actually been created.