I have a theory about the "r.h. signature".

I don’t think the "r.h." are initials, meaning they are not the first letters of the Zodiac’s names.
Note that the characters are not capitalized like names should, but written in lower case.

Still it’s a signature in a way. I belive "r.h". are the last characters of his names, not the first.

One obvious hit for "r.h." would be Arthu[r] Leig[h] Allen, the name of one of the main suspects.

After I got this idea I was thinking: What if there also was an extra "n" hidden in the poem somewhere.
I would of course make a stronger case if I had one character from each of Allen’s 3 names (r.h.n.)

So I went back to study the poem some more and I found something interesting.

Near the end of the poem where it says "…she won’t die…" right above the apostrophe I found it: An extra "n"!

In the whole poem I can’t find any other extra added character, so this "n" is totally unique.
In other words there is only 3 characters that is not part of the poem itself: r.h.n

From this I suggest The Zodiac’s real name was:

Arthu[r] Leig[h] Alle[n]

So why would the Zodiac leave strong hints to his real name?

Full of hubris The Zodiac liked to give hints and take unnecessary chances. He liked to tease the police.
Under his alias, the "concerned citizen" he states in 1969:
"Working puzzles criptograms and word puzzles is one of my pleasures."

In my opinion he liked to leave clues to his identity, but only in a camouflaged way so the chance of getting caught would be low (in fact he didn’t).
And I guess the "r.h.n" evidence would never be enough to get him convicted in a trial.

Around 1971 after the Police had circled him in, he would probably not give out such strong clues to his real name.
But in 1966 he could. And maybe he had not created "the Zodiac role" yet to hide behind, and used parts of his own name instead.

I think he wrote all 3 characters r.h.n in lowercase deliberately,
and leaves a clue that they were not initials (first characters of the names), but still a clues to his name.

Ps 1. I really don’t want to steal somenone else’s ideas or post them as my own.
I know others on the internet have noticed the extra "n", and also the idea that it may not be initials.
But to my knowledge nobody else have suggested this "r.h.n" idea before. Please let me know if this is not correct.

PS 2. Please apologize my bad English, since it is not my native language.