Valpower wrote:Your question, "Is there a meaning of milestone," is not easily understood because it is not a common construction.  I believe you are asking whether flashpoint is similar in meaning to milestone to which I would say, not substantially.
 
Thanks for the excellent description of 'flashpoint', Valpower. I couldn't have done as well meself.
I was a bit puzzled on 'milestone' too as it wasn't in the material at the quoted website though I expected it to be. 
After that figurative flashpoint, eg. miners' rebellion/troops heavyhanded repression, wouldn't you agree that the event could become a milestone on the road to workers' rights?
Possibly, this is what Wuxuanzheng meant, Valpower? 
Did you mean this, Wuxuanzheng?