The paragraph you copied from the Bitcoin wiki is imprecise.
Transactions result in transaction outputs that usually are associated with specific addresses. I.e. there is a balance of bitcoins associated with an address, that only can be spent by an order signed with the address' corresponding private key. The bitcoins itself are not identifiable, rather the path that they arrived through may be traceable.
As an example, let's assume there are two transactions:
Transaction 1: A --- 1 BTC ---> B
Transaction 2: B --- 1 BTC ---> C
A, B, and C are addresses in this case.
What the text from the wiki is trying to confer is that if somebody knew who owned address A, they might be able to force this person to tell them who owns the address B. This second Bitcoin user might then be forced to reveal the owner of address C.
However, the bitcoins itself do not have any identifiable footprint in the system, they merely exist in form of a transaction output's balance that may only be created through mining or the destruction of a previous balance.