Good grief... If you don't want people to know what you're doing, just create a different account. It's not hard, and as long as you don't abuse them you'll be fine. Trust me.
If you're really paranoid, use a Tor proxy or something.
Yeah, you'll lose whatever rep you had, but you can still ask, answer, and with a trivial amount of effort comment - so if that's all you want to do, then it should suffice.
There are a wealth of existing tools meant to aid you in remaining anonymous, and SO works reasonably well with these... I don't see why any additional support is necessary (or desirable).
If I'm missing the point, then please explain. Here's how I see it...
Anyone who visits the site is immediately presented with a great big list of recent actions on the front page. In addition to this, there are numerous views and search keywords for filtering and refining recent activity, and feeds for users who wish to keep tabs on SO activity off-site. And that's just the stuff that anyone, even users who never bother to create an account can see... Users with >= 10K reputation points get even more.
I think it's safe to say that recent activity is kind of a big deal.
Of course, I'm talking about the aggregated activity of all users on the site*, while you're talking about the activities of a single user. But what's special about your recent activity? Well...
- It associates actions that might not be otherwise related. For instance, answers about CSS and edits to DDE questions.
- It has your name/info above it.
#2 is completely under your control, of course. If you want to change your name to "SiamKing" and your picture to a bowl of tasty tom ka gai soup, that's easily done. And... #1 is under your control as well. Really. The only actions you need your primary account for are those that require rep (or mod abilities); everything else can happen on another account... or no account at all.
...And so I return to my original point: if you don't want SO to associate your actions, then stop telling it to associate your actions by using your account for everything. If you don't want SO to associate your actions with you, then stop telling it who you are!
The trolls/griefers manage to figure this stuff out without explicit support from the site; I know you can handle it.
Ok, so after a long, drawn-out interrogation in the comments, the end result of this is that you want a major change made to how the site operates to prevent a form of abuse that might occur, but isn't currently occurring, and could probably be handled on an individual basis by moderators or site-admins in the rather unlikely event that it ever did occur.
I don't see the point.
*ignoring for the time being that you can search for activity by a specific user and filter by timestamp without ever visiting their bio page; I assume you'd want that blocked as well...