follow-linkcondition, so that the link obeys
mouse-1-click-follows-link. See Clickable Text. See Buttons, for an easy method of implementing such clickable links.
Changing all the Emacs major modes to respect this convention was a lot of work; abandoning this convention would make that work go to waste, and inconvenience users. Please comply with it.
The reason for this rule is that a non-prefix binding for <ESC> in any context prevents recognition of escape sequences as function keys in that context.
For a state which accepts ordinary Emacs commands, or more generally any kind of state in which <ESC> followed by a function key or arrow key is potentially meaningful, then you must not define <ESC> <ESC>, since that would preclude recognizing an escape sequence after <ESC>. In these states, you should define <ESC> <ESC> <ESC> as the way to escape. Otherwise, define <ESC> <ESC> instead.