Is there a shortcut to getting a check on the line running to my house?

An update.  So far so good.

Derek (tech ID#509888) was courteous and professional and very much knew what he was doing.  He suspected that the MoCA filter on our line had "gone bad" and replaced that Comcast-supplied one with another one he brought with him.  (Apparently these things go bad a lot?  They seem like pretty simple devices to me.)

I am now up and running with the new gateway at the speeds that I am more or less paying for.

A couple of other things in case lurkers are interested:

Direct messages to various Comcast employees go to a mailbox or a CRM system or something; you're only talking to that one person while they're on shift.  Then someone else will pick up the thread.  It's worth mentioning because usually when you "DM" someone you are expecting that you'll be talking only to them.  In this case, it matters only because you really want to summarize the issue as best you can early so it is in your file.  I spoke with four or five reps this way.

If a tech shows up who really knows what she's doing, get her card.

@lairdjnelson

Hi there! I'd be glad to ensure that this gets looked into further. Please click on my handle (ComcastRob) and send a private message with your name, the complete service address (including city, state, ZIP, suite number, etc), and the phone or account number, and any pertinent details-- like the ticket number(s)-- so we can help. 

I've sent two messages to ComcastRob, who, to be sure, has no responsibility to me or this issue, but I wanted to mention that I never heard anything.  Again, not his job; I totally get it.

I called Comcast who is sending me a new modem in the mail that I will continue to be renting and for some reason charged me $15.  While I was on the line trying to get this technical issue dealt with they also tried to upsell me cell service.

The replacement modem is cheaper than the $40 they will charge me to roll a truck, so I'll start there even though that's almost assuredly not the problem since as mentioned my cable tv quality is also garbage at this point.  But the modem needs an upgrade anyway so maybe it will somehow be better at latching on to an upstream signal.

To be fair to everyone involved the customer service/upseller was very nice on the phone and I have no problem with him.  He was clearly mortified that he was expected to try to sell me mobile phone service while I was standing in the rain outside a sushi restaurant that had WiFi since my connectivity has now become flaky at home.  This company has some serious issues it needs to work out.

We'll see what the new modem does.  In the meantime my kids will do online school in the car somewhere where there's a reliable signal.

Followed the new modem setup instructions to the letter. I started by setting it up where the old one currently lives.  It sat there and blinked for 20 minutes (the setup guide says to wait for 20 minutes, so I did).  Plugged the jack straight into the wall; waited another 20 minutes (blinking light again).  Moved it all the way to where the cable enters the house; tried it there.  Waited for 20 minutes.  Blinking light again.  Plugged the old modem back in in the original location and am now getting 0.3mbps download speed (while paying for 200).  Now time to get billed $50 for a tech visit and to waste a day on the phone explaining why my new modem order has to be canceled and to find out how to send it back.

Hello, @lairdjnelson! Thank you for the update, and letting us know you're still waiting on a reply to your Private Message! I was able to locate it, and replied to you over Private Message. Please reply to me there once you get the chance. Thank you! 

Done; thanks for looking into this.  I'll keep this thread updated as Comcast makes progress.