So to follow that link then
sudo setcap 'cap_net_bind_service=+ep' $(eval readlink -f `which node`)
should do it (for Linux) - sets the node.js executable to be able to do this.
To follow up on the running as root... while probably not the end of the world on small single user systems it generally considered a bad thing to run services that are quite as powerful as Node-RED as root as they could be corrupted and wipe disks, install bad apps, etc as they have full admin rights to the machine... From the Node-RED perspective the main issue is that the user directory is now the root user's directory rather than the existing user's - so users then say "where are my flows" - or "I can't find a node I installed" etc. You can instead start Node-RED with the -u {user-dir-name} parameter to force it to where they are...
