Even if UASF will create altcoin then be it.
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I will use BTC as store of value and UASF to play casinos, pay for stuff. Same time let original BTC be original BTC.
You don't have a clue. UASF won't split it's a softfork. Some stupid miners like jihad and BTU bovine can ragequit and create their altcoin BTU, but it will be just alt like LTC, no more
The main point of UASF is to begin SegWit before it gains a significant majority of miners. If, when it occurs, SegWit has a minority of hashrate, there will be a split.
In any case, there needs to be a minority of miners that decides to split off, and make a pure-segwit prong forking off. If they don't, your UASF node will not find a "pure segwit" chain, and will just stop. So, as a user, starting up a UASF node BEFORE a minority of miners decided to fork off on a pure segwit prong, leaving the main chain behind them, serves no purpose, because your node will simply *not find any valid chain out there*.
The error in thinking is maybe that such a node will only pick the segwit-signaling blocks on the main chain. But that cannot be the case, because that would mean that that node does accept intermediate "invalid" blocks, as the segwit-signaling blocks are not consecutive. As such, an UASF node that would accept, but not "interpret" non-segwit blocks would just forfeit all transactions in those non-segwit blocks. If I pay you with a non-segwit transaction, you would never see my coins arrive.
As I said, this is going to be a very entertaining spectacle.
Probably the best thing to do is not to touch one's bitcoins during the whole time of settlement (if ever it settles) ; or simply to exchange them for exchange IOU on an exchange you trust, but not keep them on the funnily dancing block chain and certainly not on one prong or another.