• sed requires both ( and )characters to be escaped (in ERE mode), whereas grep and awkdon’t require ) to be escaped.
• sed requires { to be escaped (in ERE mode) even if it isn’t part of a valid quantifier syntax, whereas grep and awk don’t require escaping. For example, you’d need \{a} in sed whereas {a} is enough for the other two.
• In BRE mode, grep and sed don’t require ^ and $ to be escaped if they are used away from their customary positions.

Fuck that.

Edit: I’m not complaining about the the page, it looks nice and polished. It’s the inconsistencies among the GNU tools in handling regex that grind me.