I know I've seen TER clients talked about there a lot.
In fact, they are called Slobbyists.

Im sure they will let you join with taking the usual test. Dont forget to ask for the free T shirt too.

If you have access to the Providers Only Board you could bring up your topic there. Seems to me Blacklist (the one on the web not your own personal blacklist) should be used for dangerous clients or rip off clients only.

The best way to review clients

is simply to ask other providers. Most clients will willingly provide references. I just had a client who came up clean on his profile but by talking to a couple of providers that he had reviewed, it came to light that he was much more rough than I wanted to deal with and thus I didn't think it was worth the risk to go through and make an appointment. It takes more work, but it's worth it. xx

but i wont disclose it in here. Not as detail, just like safe, ok, would meet again.  

you can contact me in private tho.