Anyone can easily verify that this account was created by @yabapmatt on any Hive block explorer and be assured that it is really my account.
And then it was also upvoted... but still it could be upvote trail or other voting service.Well, not really. One can easily go and check, that indeed @yabapmatt.sps was created by @yabapmatt, but that could be exploited if there's an account creation service where @yabapmatt account is account creator.
So actually a proof good enough was a comment you wrote using @yabapmatt account.
Anyway, good to see you around posting :-)
Good luck!
His official account shared or reblogged(as they say) this post. That was all the proof I needed.