sys.comcast.net has no TXT records.
Question and response
Question
dig sys.comcast.net. TXT
Answer
The response has no answer records.
Authority
sys.comcast.net. 900 SOA dns101.comcast.net. dnsadmin.comcast.net. 933448 7200 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0