Greasy Fork

Good idea!

Seems work perfecly!
Just an observation :
It's possible to add an hover state on the Icon that's confirm the copy ?
The icon go away too quickly, so it's possible to forget we have hover it and copy something...
I know, that's no very clear...
;-)

Maybe something like that (with CSS only):

/* ==== 0-GM - Hover_Autocopy tweak v.1 === */
#copytext_icon[style^="display: block;"] ,
#copytext_icon[style^="display: none;"]  {
display: inline-block !important;
background-position: center center !important;  
background-size: 30% 30% !important;  
border-radius: 100% !important; 
opacity: 0.05 !important; 
border: 1px solid red !important;
background-color: gold !important;
transition: all ease 0.7s !important;
}

#copytext_icon[style^="display: block;"]:hover  ,
#copytext_icon[style^="display: none;"]:hover  {
background-position: center center !important;
background-size: 60% 60% !important;
border-radius: 100% !important;
opacity: 1 !important;
border: 1px solid red !important;
background-color: red !important;
transition: all ease 0.5s !important;
}