To be fair that discussion about dropping support for IE9 took place over 18 months ago — that is a long time in browser age. Bootstrap is following in the foot

To be fair that discussion about dropping support for IE9 took place over 18 months ago — that is a long time in browser age. Bootstrap is following in the footsteps of a bunch of other JavaScript libraries and frameworks that dropped IE9 (so all the arguments are pretty much known), and by now IE9 is that much more of a marginal browser that supporting it is in no one's interest. Ember certainly has a very pleasant way of discussing these matters, and for dropping support for IE10 or IE11 that would be a fair way to do it now at the end of 2016, but there's just not much to be gained from a discussion about dropping IE9 support at this point.