Security Considerations section notes

[noncombatant]

"It is RECOMMENDED that an user interface" → "...a user interface"

"Such an interface would allow an end user" → "...SHOULD allow"

Add: "The interface SHOULD represent serial ports in a way meaningful to the user. (For example, device serial numbers would not likely be meaningful, at least not on their own.) Standard names, like COM1, and device manufacturer names, are more likely to be meaningful."

"A user agent SHOULD allow the user to select from all serial ports available on the machine, and be shown an indicator for serial ports that are currently busy," → "...on the machine. Additionally, the UA SHOULD show an indicator for serial..."

"It is also RECOMMENDED that user agents provide users with a means for the end- user" → "end-user" (no space)

"to view which independently of any access request," → missing words? I don't know what you meant here.

"and be given the ability to revoke individual or complete access to serial ports at any time either at the user agent level or per origin [HTML]." → do you mean something like: "The UA SHOULD give the user the ability to revoke 1 or more origins' [HTML] access to any or all serial ports at any time." ?

[noncombatant]

Also, add: "User agents MUST make WebSerial available only to Secure Contexts."

[marcoscaceres]

These would make for a great pull request (hint hint @noncombatant ❤🙏😬)