HT6114 OS X Mavericks v10.9.2 Update - How do you block incoming iMessages from individual senders?

Question

Just trying to figured out how to block individual senders on iMessage (blocking feature added to 10.9.2). I thought that an option would exist in the application by going to the "Buddies" menu but alas, the option is greyed out on both my systems after the 10.9.2 update.
The help file associated says to
Select a conversation in the sidebar, or a buddy in your buddy list, then choose Buddies > Block.

Answer 1

A quick summary.
In Messages menu > Preferences > Accounts > iMessages account which now has a Blocked tab.
The Messages > Buddies Menu > Block only applies to AIM Accounts
You can also block them by name in Messages > Preferences > Accounts > AIM accounts Privacy tab > Block Specific People List button (Block by Screen Name)
Jabber Buddies are effectively "blocked" if they are not Authorised (to be a Buddy).
See also the Buddies Menu.
Many of the Menu items refer to iChat Actions which is the backbone of the app.
8:59 pm      Thursday; February 27, 2014
​  iMac 2.5Ghz i5 2011 (Mavericks 10.9)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad