There's another large gap in posts from April 2015 to April 2016. I don't see any difference in the quality of English from before and after the older gap, but the gap from 2016 to 2017 does result in a significant change. For example:
If you are new to trade its is better to trade with bitcoins because altcoins are more unstable than bitcoin if you start with altcoin you may lose your investment.So bitcoin trading is more safer and then don't be in a hurry you need to have patience to be a good trader but you need to improve your skill on decision making because in trading you have to act according to the market price.But before start trading do lot of search or you may be lose your investment.
A native English speaker would never write "bitcoin trading is more safer," regardless of how lazy he was at applying the written language. And the lack of punctuation is another telling sign, although some native English speaker can be quite lazy about punctuation when writing.
The original post definitely seem to come from one who is a native English speaker, or at least one who's been well educated in the use of the language.