The key decrypted:
ABBAABBAAA AABAABAAABBBBBABAABAABBAAAAABAABBABAAAABBBAABBAB

MY REPUTATION

This is a bilateral substitution method, applied partially. (bacon cipher)
It would have normally been used like this:

steem

BAABABAABBAABAAAABAAABBAA
(following, the capital letters represent a "b", all the others an "a")
=
BAA BA BAA B BAA BAAAA BAAA B BAA
Tim Is Mad! I Saw Blood. Jack A Saw.

So:
Tim Is Mad! I Saw Blood. Jack A Saw.
= Steem

But I believe Tim watered it a bit down for the sake of competitivity, go on... Keep on working people!.

PD: @timsaid's reputation at this moment is 61, just in case it changes.