Is tail removal something that's still on the table as a future upgrade now that the urgency to stabilize the difficulty algorithm is over?

A maximum block interval as well as a guarantee that the chain will always advance as long as there's one person on the planet willing to mine it is a very nice feature to have.

AFAIK Bitcoin Cash is planning to have a set of non backward compatible periodic protocol upgrades (aka HF), let say one every 6 months or so.

So I guess that

@theZerg's

tail removal is something that is definitely on the table IMHO. Wonder what

@dgenr8 @deadalnix think about it?

Another really interesting proposal is

Bobtail. It has ben presented at Scaling Bitcoin Stanford by Brian Levine (Umass, same author of the

Graphene paper).It is a generalization of the current Poisson process to minimize mining variance.

It is orthogonal to a difficulty adjustment algorithm but contribute to remove outliers from the process. Quoting the abstract from the paper linked above:

Bobtail paper - reducing variance - said:

Our algorithm, called Bobtail, generalizes the current algorithm by comparing the mean of the k lowest order statistics to a target. We show that the variance of inter-block times decreases as k increases. If our approach were applied to Bitcoin, about 80% of blocks would be found within 7 to 12 minutes, and nearly every block would be found within 5 to 18 minutes; the average inter-block time would remain at 10 minutes.

Other than reducing process variance it even reduce the profitability of a selfish mining attack significantly

Bobtail - hinder selfish mining profitability - said:

Further, we show that low-variance mining significantly thwarts doublespend and selfish mining attacks. For Bitcoin and Ethereum currently (k = 1), an attacker with 40% of the mining power will succeed with 30% probability when the merchant sets up an embargo of 8 blocks; however, when k ≥ 20, the probability of success falls to less than 1%. Similarly, for Bitcoin and Ethereum currently, a selfish miner with 40% of the mining power will claim about 66% of blocks; **however, when k ≥ 5, the same miner will find that selfish mining is less successful than honest mining.** The cost of our approach is a larger block header

emph is mine, if true this basically means that the selfish mining problem is solved for good.

Still need to study the paper but it is indeed promising.