Chances are that if you have an IP6 address, then you are probably much more identifiable than if you stick with IP4. This is because it is less likely that an IP6 address will be re-allocated. You will either have it forever,, or at least for a good long time.
But even if you are using a temporary IP4 address with NAT, your ISP will probably be able to identify the account holder and probably the physical location of the point where it touches their infrastructure, just as long as they take account of timezones and DST correctly!
Although I don't agree with it, the presumption is that they could profile a person who was becoming a risk by reading their blogs, forum posts, browsing history, email, IM and SMS messages and even purchasing history (how did you buy your machete), and once identified, single them out for even greater surveillance. Once under surveillance, they can be caught before doing any damage.
But this effectively means that they will need to watch all people who match certain criteria, including many who aren't, and never will be, a threat to society. It's a really difficult problem which will always upset some people on one or other side of the argument.
My view is that as soon as government agencies have the ability to look at what people are doing without sufficient safeguards, they then will eventually abuse that ability, and look for things that have not been sanctioned by this legislation. Anything. Being a member of a particular political party or religious group. Or an anonymous blogger about personal freedoms. Or an infrequent copyright infringer. Or harbouring anti-AGW thoughts. Or being upset with your local MP. Or a consumer of legal on-line porn. Or an objector to HS2. Anything.
Is everybody who supports this charter sure they are squeaky-clean?