��

is performance so critical that using $( rather than '('
gains a lot?

There's visual gain that I've mentioned. If you replace $( with '(' then my argument about visibility fails. $( is very distinct.

��

Maybe it is also a useful pattern for markup languages:

�� aStream between: '<HEAD>' and: '</HEAD>' putAll: [
�� ... nextLevelIn ... ].

I don't think it's a good practice to generate individual tags by hand, you should have more abstraction.

Pillar has

PRHTMLTag>>with: aString

stream << $> << aString << '</' << name << $>

Apart from it being hard to read due to </> it's so simple that it doesn't matter and you have little to no gain in trying to make it "nicer".

Peter