It is definitely useful.You know the spam bots which are created to open trash topics on bitcointalk can also be programmed to use that Report to Moderator function which is a bit heavy operation on the server end.
Do you think I'm a spambot who tries to overload "Report to moderator" function
. Trust me I'm not.
Hence the restriction applied to anything that is going to result in an action which GET/POST data to the server totally makes sense.
The thing I didn't makes sense is that why we are ristricting good members good behaviors as a solution for a spammers bot programs. Why can't we introduce a separate system to identify the user wether bot or human instead demotivating well wishers of the forum.