About punctuation: what you say is interesting, but I have always regarded punctuation as an essential element of grammar. Of course this is a recent development, tied to writing rather than speech, but very important, and now surely indispensable.

I stand by what I wrote. Spelling and punctuation are important, but not a part of grammar.

The thing about the old puzzle you pose is that it can be understood without any punctuation at all.

"Caesar entered. On his head a helmet, on each foot a sandal, [and] in his hand, he held his trusty sword."

There is nothing ungrammatical about the unpunctuated version. If I reformatted it in a difficult to read font, it would still be grammatical. Also, the sentence "Caesar entered on his head, a helmet on each foot, a sandal in his hand he held. His trusty sword to boot." is also grammatical but improbable.

Ceci n'est pas un seing.