I'd say, Banque Worms ruling as we've found out can always be at play. Cough $900,000,000.00 accidentally transferred a couple years ago from a large bank to lenders.
By this definition, isn't for example USD a ponzi? Afterall, it is a Fiat currency now and not backed by a commodity. If I received wampum back that would offset it no? How does taxes/gdp protect you if taxes are of their self made up of USD.
Also, you can leverage the ISO/IEC 2022 extension and represent them with Caret Notation. Note: recommend an escaping mechanism depending on data. REF: https://en.wikipedia.org/wiki/C0_and_C1_control_codes#C0_(AS...
An editor such as vim or pager like 'less' will display them. You can also 'cat -v' a file.
I would argue Agile is a Philosophy and Waterfall would be more of a Methodology. My biggest concern with Agile is that it's lacking integration with a methodology (ie: best practices of waterfall could be in an agile way). Companies and teams tend to just say lets do Agile/Scrum/Kanban and leave out the requirements definition, documentation, etc and replace it with "As a user create shiny button". Which, might be fine in some cases but as a new-start it lacks direction IMO.
You can already do this with `write` which is in most linux distro's. Make sure `mesg` is set to y then test with `echo "hello" | write <username>`. `Wall` messages all logged in users and I wouldn't recommend that approach.