#2. non-fungable. We like to think of bitcoins as being fully fungable. But the reality is that any bitcoin wallet/coin can be black-listed or otherwise "tainted". Your wallet could be black listed for any reason, or by mistake with no recourse. Black-listing means that anybody can create a list containing your wallet address, and then any bitcoins in that address, OR, any bitcoin that ever TOUCHED that address can forever more be treated differently. If YOU are found to have ever "touched" a black-listed coin, or coin from a black-listed wallet, you could then be targeted, hunted down, your real world accounts/property froze/taken; you arrested, who knows what. Regardless, not all bitcoins are perceived to be "equal". And, EVERY bitcoin has a history trail (moving from wallet to wallet) that anybody can easily follow see #1 above.
Bitcoin can never really be great unless every coin is truly fungable. AND, to be fungable then coins must not be trackable. Yes, some "alt coins" try to deal with the above. But ALL mainstream cyrpto currencies especially BITCOIN need to start taking these issues seriously.
Is there a way to make bitcoin non fungible? I don't think so, if you want to erase the history then you should use the coin mixing service so you will be getting bitcoins from some other source but wait why we need to think that bitcoin is always connected with dirty hands? when the adoption comes then everything will change.