set `user-select: none;`

apps/app/src/components/ReactMarkdownComponents/Header.module.scss

@@ -7,6 +7,7 @@
   .revision-head-edit-button {
     margin-left: 0.5em;
     font-size: 0.6em;
+    user-select: none;
     opacity: 0;
   }
 }