Surely the difference between 0.999R and 1 is practically non-existant and philosophically massive?
Nope, they're completely the same, philosophically and otherwise.
It is the difference between claiming complete certainty (for example) and always allowing for the possibility of that which is unexpected (no matter how likely or unlikely). It is the difference between an obtainable destination and that which can never exist or be obtained in reality.
Nope. There is no uncertainty, 0.9999~
is 1. In fact all decimal representations are infinite sequences, it's just some of them finish in an infinite number of 0s. This is not, as it may sound, a cute aphorism but actually fundamental to the construction of the real numbers. Real numbers are
limits of inifnite sequences.