This section was confusing.

So what's this serial communication? It's an asynchronous communication protocol where two devices exchange data serially, as in one bit at a time, using two data lines (plus a common ground). The protocol is asynchronous in the sense that neither of the shared lines carries a clock signal.(...)

0. "serial communication? It's an asynchronous communication" reads like all serial communication is asynchronous. I am not sure is intended? (it does not seem so from the Wikipedia link itself.)
1. Serial communication (sync or async) does not seem a protocol (it is also not stated as such in Wikipedia).
   • It seems a mode of communication (bits sent serially). Many different protocols could be implemented on top of this general idea, or not? These are all serial protocols albeit not all async.

Today's computers don't usually support the serial communication protocol, and even if they do the voltage they use, ±5..12V, may be higher than the micro:bit will accept and may result in damaging it. You can't directly connect your computer to the microcontroller. (...)

2. USB is a serial protocol and is supported by most modern computers (contradicting second paragraph), though it may not be async.
   • But "the serial communication protocol," hints that you have a specific serial communication protocol in mind, not all of them (maybe USB or UART, or RS232 since you start with DE-9).
   • Could you explain which serial communication protocol(s) are you including vs excluding, or thinking about?