I had a short conversation with a person who works at an ISP provider

[Buffer Overflow]

This person works at an ISP provider in South Africa

He/she might be the one that makes the tea/coffee.

[Rannasha]

Seems pretty unlikely, no?  I've talked to employees at Boeing who have no idea how a plane flies.  Maybe that's what's going on here?

Probably. Once the company you work in is large enough, it's fine to have very specialized employees that only know their specific tasks and not much more. A radio/communications engineer at Boeing doesn't have to know how the thing flies, just how the crew can talk with others. A sales rep at an ISP doesn't have to know what ports are and how they work. Of course, you run into the situation where such employees have vague and incorrect ideas about how these things work and then suddenly gain undue credibility because of the company they work at.

[tvbcof]

...
I'm really surprised that everyone that has responded so far seems to have just accepted this is true. I suppose even if it's not true, it's still helpful/useful to consider how resilient Bitcoin would be if someone did actually choose to do it.

Bingo!  Since we are talking about a financial system which we hope people can feel confident relying on to store and utilize value it some quantity it is more critical to consider a wider range of attack surfaces than would be the case with other applications.

There is also the fact that any nation's monetary system is a hugely important facet of the state's function.  So, an alternate system which could challenge the official system could be a significant threat justifying a significant response.  Problems here would be triggered more my a weakening of the official system than by a strengthening of alternate solutions, and and economic or currency crisis would be accompanied by a lot of extra-normal policies.  A clamp-down on freedoms of access to the global internet would probably be a lesser of the multitude of complaints.

The use of packet filters and protocol recognition and disruption is common to control people's behaviors within organizations.  It seems (to me) not much of a stretch to project that it could happen at the direction of a nation-state level when a compelling need arises.  There will be a golden period of time when it is quite effective since it will spur a lot of interest in developing work-arounds.  For this reason it is good policy to wait until a crisis situation for any real use so that people are lulled into a belief that since it has not happened yet it never will.  Or more typical; "What is packet filtering?"

[waxwing]

Packet level filtering will not ultimately work in stopping Bitcoin I think, although it could well be tried and may even be a catalyst for dramatic changes in society.

Attack 1: filter Bitcoin protocol
Response: encrypt, e.g. using vpns, secure tunnels, ssl connections

Attack 2: restrict use of encrypted connections to "trusted" sites (not easy to do fully, and a devastating attack on internet freedom, crippling a lot of activity).

Response: perhaps move to a steganographic approach. Hide bitcoin data in plain sight (even in html pages?).

Attack 3: revert internet to a limited "walled garden": customers allowed only incoming connections, can only access government mandated hosts.
This is a dial back to something worse than mid-90s internet which is nearly unthinkable right now. Note that even China allows a lot more than this.
Response:
Meshnets? Revolution?