I just spent the better part of an hour seeing if I could compose a coherent blog post from my phone. This is not that post.
First I should say, the phone's hardware is not the culprit. The Nexus 6 with Swiftkey is a lovely piece of texting hardware. Even a two-sentence email may be essayed.
But while it is obviously possible to compose a blog post on a phone, it is yet another exemplar of the principle:
Just because something can be done does not mean that it should be done.