Maybe time to learn the ISO date format YYYY-MM-DD.

They are likely to use some kind of block list service. So if you can find out which service that they are using you can get on.

There is also a possibility that Comcast do a "man in the middle" intervention on your mail traffic that you aren't aware of yet. Check the IP addresses that can be involved, and if you have account on servers elsewhere it might help.

But often whole net blocks are marked as dynamic addresses in anti-spam services even though they aren't.

It depends on the tip if they investigate it or not.

A single tip may not be a case for action, but it may still be useful to raise awareness of that something is going on.

If more than one indication comes in then the tip may be useful.

Don't target the marketplaces, target the vendors on the marketplaces.

And how can the vendors on a marketplace be sure it's not a federal honeypot?

That's why you have some review features of a document.

However it is proven earlier that even deleted text often lingers around in the Microsoft Document file format, so the only way to make sure that you come clean is to only publish as a PDF.

In addition to this - use some kind of "keyword" in your texts for sections that you need to revisit when writing. Use a word that's unlikely to be in the final document that you can search for.

And even when you write - don't use words like "crappy" unless actually referring to fecal matter, use a more civil word like "questionable".

They just need to monitor 4chan.

In which case it may mean that what happened is that the authorities did set up at Tor node, then tagged the packets and sniffed them on their way to the destination.

Essentially - any system where the intruder have access to the majority of the network is vulnerable, no matter if the information is encrypted or not. The conclusion is that if you are going to run questionable stuff, then you need to put a server in a country where the legal system is corrupt and you pay them to look the other way. If your business gets big enough it won't help since then that country might be cut off from the net.

4. License to be a politician.
5. License to procreate.

The problem as I see it is not the authorities, but that if you have an unusual name and have opinions that aren't popular in one camp then you run the risk of getting harassed. Even if your opinion is legal and acceptable you can still run this risk. You will only have to go as far as a political opinion that can cause trench warfare. Like Obamacare.

Some people have the tendency to focus more on you as a person than on the issue.

The end result will be that people won't dare to publish their opinions due to the risk of being followed, getting their property damaged or worse.