Spelling this out just for kicks.
Suppose you own 1 BTC: you presently own a 1/16.6M share of the World Wide Ledger (if you hold forever, this eventually shrinks to a 1/21M share). There is a fork. One one side is BitcoinA, in which nothing has changed. On the other side is BitcoinB, in which emission has doubled. As
@Zangelbert Bingledack points out, this event alters *not one bit* your 1/16.6M share in BitcoinA. In addition, you now also hold a smaller (and faster decreasing) share of BitcoinB. This bounty you may sell or keep.
Yet, undeniably, there are more cryptocoins post-fork than before; in this sense, there is less digital scarcity. But is this a problem for you? Obviously not if the price of BitcoinA is unaffected or increases. It would be a nuisance, though not a loss, if the price of BitcoinA permanently decreases but the loss is made up by gains in BitcoinB. The situation only poses a definite problem to you if the combined valuation BitcoinA + BitcoinB becomes permanently smaller than the pre-split valuation. How likely is this?
1. Either there is a compelling economic case for both BitcoinA and BitcoinB, or there isn’t.
2. If there isn’t, one of the two coins withers. If it is BitcoinB, you are were you started. If BitcoinA withers, you are covered, as you hold a significant stake in the winning coin (indeed, the highest possible stake you were prepared to hold), which events have demonstrated to be stronger than the pre-fork one.
3. But scenario 2 is unlikely or not interesting: if there hadn't been a compelling economic case for the fork, it would not have occured, or it would be unnoticeable. We may therefore assume that all the prefork use cases continue to exist, plus whatever new ones that were not served pre-split. Under such conditions the combined valuation of BitcoinA + BitcoinB > the valuation of pre-fork Bitcoin. The split created new value. Wealth was generated. You win.
4. The only worrisome situation (“Back’s bugbear”) can be one where the combined valuation of BitcoinA + BitcoinB < the valuation of Bitcoin pre-split (this also covers the special case of 2. where one of the coins go to 0 and the winning one ends up being weaker than pre-split). Why would this happen? Conceivably, if the disorder created by the fork is so great, the panic so widespread, thad cryptocurrency never recovers.
You be the judge of how likely 4 is. But if you are worried about it, you should get out of crypto. Forks are built into the system, as they are to any open source project: their possibility constantly orients the direction the project takes, exerting healthy pressure, weeding out malinvestment, preventing against co-option. Indeed, Back’s bugbear is a threat only to people like Back, who would like to assert control of that direction. When Back speaks of a “contentious hard fork” he only means: a fork that takes me out of the driving seat.