I was under the impression it was supposed to be obvious. The commentary on Grantland referred to Ligotti several times when discussing True Detective.
Other than the "time is a flat circle" line and his commentary on suicide, little of what Cohle said was all that memorable. Marty Hart's retorts were the better lines. The best line went to the former teen prostitute turned cell phone salesperson!
To me, the most truly memorable moment was the 6 minute long take at the end of the fourth episode.
I found the opposite to be true. The Cohle character made the show for me. They could have gotten rid of the other guy entirely.