I perfectly agree with this.
I have spent some days to figure out what was wrong with my DKIM failing checks and now the answer has finally come.
The vast majority of users couldn’t care less of adding disclaimers at server level (which can be always added at client level) and DKIM not validated is a serious show-stopper for most big companies like microsoft and apple (try mailing @outlook.com and @me.com with a rotten DKIM).
Also, putting “MaximumSignedBytes 1” looks like a good receipt for catastrophic results, as antispam contraints are being made stricter and stricter every day. Imagine a flood of such mails being received, and clearly see the provider mass blacklisting domains in zero time.
So now the question is: waiting for an official correction in 7.5, how can one deactivate the “add disclaimer” feature, considering that, in my case, it was never activated?
Second question: are you sure that is it only that feature that fiddles with DKIM validation?