Thus I figure there's probably some general guidlines here about which pins one should avoid or reserve for special uses. I'm still trying to figure out when I can use gpib0 and gpib15 and 16 safely. gpib1 is also a landmine for input because it's TX output and RX is a landmine for ouput and moreover it's pulled up externally.
thus I was hoping there was a list of GPIO lines and their frequent idiosyncracies.
Also since you seem to be knowledgable about boots and such I'll mention I'm struggling with the HUZZAH in trying to figure how to use DTR from an FTDI Usb-serial board to let me upload without the fiddly flash and reset button presses (like the nodeMCU does).