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AM, pleases not that "fee market" should be plural, as both in- and out-of-band fee markets are needed to efficiently allocate the scarce resources of the network.
All the FUD about BTCC is overblown. Peter Todd already said RBF makes this mostly a non-issue, and Lightning will make us forget it ever happened.
The Gavinista big block fetishists (having lost their XT node/block/governance war) are just using anything available as a cudgel to beat up on Team Core, no matter how far fetched (because their intended audience is low-information redditards and MBAs, not True Bitcoiners).
Sure. Here is how the out of band market works. The fees in Bitcoin keep rising as growing demand hits the 1 MB blocksize brick wall. When the fees get high enough people start switching to Monero that does not have this problem. Then Monero becomes the dominant coin and the fees in Bitcoin fall as nobody really cares about Bitcoin any more. This is basic economics. If Monero does not step into the opportunity somebody else will. DASH for example cannot be faulted for at least trying.
It's a given that with relatively small blocks the Bitcoin main chain would not be place where most transactions are done (obvious). It isn't a given that means transactions would then move to Monero or Dash (or LTC or DOGE). They could in theory move to Bitcoin side chains or Lightning or something else closer to the Bitcoin sphere.
That still leaves the issue of what happens if the Bitcoin main chain has hardly any transactions as the block rewards run out. A small but highly-secure chain that serves as a monetary anchor for other transactional systems rather than as a platform for transactions directly makes much more sense if the rewards don't diminish down to nothing, but there is really no way to get there with Bitcoin's fixed supply.