Is this in response to someone in specific?
Because I see mostly classical Keynesian posts here (which is what used to be call "mainstream economic theory" up until pretty damn recently).
Keynes wasn't a Chartalist, though. Indeed, he actively considered himself to be a classical liberal, something which Hayek was confused about during their letter debates. He suggested using deficits to increase demand, but not that this was universally possible, or that the government "can't run out of money you yourself create" as has been said at least once on this page of this thread. Whilst tautologically true, it's basically irrelevant. I can't run out of CyclopsRock dollars either, but if no one wants them, they're useless. the US economy is large and powerful, but only a fool would suggest that deficits literally don't matter, which appears to be the logical extension of the "you can't run out of money you print" argument, nor did he advocate removal of the bond system.
Likewise, to the "they're basically paying us to take their money!" re: negative interest rates, that's true, and only a silly billy - be they private or public - would ignore an offer like that. It's worth noting, though, that by far the single largest holder (and increasing, not decreasing, as a share of debt - up almost 3x in the last decade) of US bonds is the US government itself. This has the benefit of pushing down the interest rates of the other, foreign holders (as well as domesticate ones like pension funds which, obviously, suffer from negative interest rates), but also means that those arms of the US governments that buy its own bonds will lose out when they get them repaid at negative interest rates. Given this is such a large portion of the debt, the perceived gains from this negative interest rate is significantly lower than it appears on the surface.
But, further to this, it seems that this is offered an argument to continue with public spending. The problem with this is that, short of building a lot of infrastructure, this encourages the production of structural deficits - which, again, when you're having other people pay you to take their money is OK, but structural deficits aren't easy to remove. If you
do take a look at Greece (and I'm not drawing a comparison with the US here, but we can all learn lessons), it used debt to bolster it's GDP for about a decade. It's GDP rose almost exactly in line with its debt for its first decade in the Euro - so the economy itself really didn't grow at all. Its wages also rose in real terms, as well as its public welfare programmes etc. The problem is that it wasn't actually producing any more - indeed, it's increased wages actually caused its international competitiveness to go down. Its started cutting now - which has had disasterous effects on its economy - and it's GDP has fallen, but it still hasn't fallen as far as it grew since it's adoption of the Euro; A place it'll inevitably end up in, as it's real economy has not grown in that time. This highlights the problem is using temporarily cheap credit (as Greece's was from the ECB, after their own high rates with the drachma) to fund not infrastructural projects, but ones that need constant payments - that credit won't always be there. A better use for the money, therefore, in my view, is to either earmark specific parts of it to specific bits of infrastructure, or to fund tax cuts to the lowest paid (and then work your way up - in the UK now, anyone earning under about $14k doesn't pay any income tax at all, and that ceiling is going up still). These both have the effect of increasing demand without offering long term liabilities to the government which do real harm when they are later removed.