This is your friendly neighborhood IRS tax examiner chiming in from work to say:
This is all totally accurate, and I just pulled this post out of my queue because I've got one of these on my desk right now. On the taxpayer's Schedule C, the self-employment income form, where people put their kind of business or profession, this individual has written "Unnamed activity."
That could be anything, from something legal but salacious to something that would lead to a long prison sentence, but per IRS policy I don't care, and it's none of my business.
As my delightful supervisor is wont to point out to one of my more pedantic coworkers, we're neither auditors nor the number police; our job is to mainly to care about if a tax return is cleaned up and ready for data transcription. I make sure a return is signed, that numbers are on the right lines and all the forms needed are present and in the right order. I also write down codes to indicate when specific forms or conditions are present, and I flag things for other departments like identity theft and certain kinds of fraud. (A note for people afraid of the IRS: I'm specifically looking for kinds of fraud that it's impossible to commit by accident or through well-meaning ignorance.)
My "unnamed activity" person's return doesn't have anything for me to code or flag: it's signed, all forms are present and filled out correctly, there are no suspicious or improbably large deductions, they're not trying to argue they're a sovereign citizen and the IRS is illegitimate and/or has no authority under blah blah blah deranged argument. They filled out the form to pay self-employment taxes, correctly, and they filed well before the deadline and paid their tax bill in full.
The IRS has no reason to go after this person, and they won't, because the IRS largely doesn't care about crime beyond the various flavors of tax fraud. It's actually mind-boggling just how much the IRS doesn't care about, even with things that seem to very much belong in the tax fraud category. I know a lot gets sorted out further along down the processing pipeline but yikes.
Unrelatedly, it's an extremely good idea to file as early in the tax season as you can, and to also get an Identity Protection Pin before one is eventually assigned to you, because the amount of identity theft and fraudulent returns I've seen in the last month alone has been enough to make me daydream fondly about mass extinction events and how much humanity deserves one.
Anyway. I see one or two returns like this a month, and it's never a big deal. I save my time and energy for the modern day robber barons who send in dictionary-thick monster returns, because it's the least I can do to flag the loopholes they can't resist trying to exploit.