I'm seeing this too with the rig I have on my office on a cable modem. It may not be a Comcast issue, however, as from that tracert in the link you posted, at hop 10 the traffic is leaving the Comcast network and jumping over to Qwest/GBLX. It goes one more hop (again, on Qwest's network) and then it fails.
Here's the tracert to the same IP from my end:
C:\Windows\system32>tracert 72.165.61.138
Tracing route to 72-165-61-138.dia.static.qwest.net [72.165.61.138]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms fitesip01.fites.lan [10.0.0.1]
2 * * * Request timed out.
3 9 ms 16 ms 11 ms GE-1-2-ur02.hersheymills.pa.panjde.comcast.net [68.86.156.253]
4 7 ms 9 ms 14 ms 68.86.153.121
5 8 ms 7 ms 9 ms te-9-1-ur01.lowerpaxton.pa.panjde.comcast.net [68.86.208.197]
6 8 ms 9 ms 11 ms te-8-1-ar01.lowerpaxton.pa.panjde.comcast.net [68.86.208.193]
7 13 ms 12 ms 11 ms 68.85.158.186
8 12 ms 21 ms 13 ms 68.85.159.229
9 13 ms 14 ms 14 ms be-40-crs01.401nbroadst.pa.panjde.comcast.net [68.86.208.33]
10 31 ms 18 ms 16 ms pos-1-9-0-0-cr01.mclean.va.ibone.comcast.net [68.86.90.13]
11 18 ms 21 ms 18 ms TenGigabitEthernet3-2.ar3.DCA3.gblx.net [64.213.33.57]
12 20 ms 18 ms 19 ms te1-3-10g.ar2.DCA3.gblx.net [67.17.108.145]
13 51 ms 18 ms 18 ms qwest-1.ar2.DCA3.gblx.net [64.208.110.30]
14 * * * Request timed out.
15 106 ms 105 ms 105 ms tuk-edge-06.inet.qwest.net [205.171.11.22]
16 * * * Request timed out.
17 * * * Request timed out.
18 * * ^C
C:\Windows\system32>
I've found that this is the same IP my Steam client is trying to connect to also.