On more than one は in a sentence

Question

When is it okay to have more than one は in a sentence? I've come across a few examples where there have been more than one は, and hadn't why.

Example:

日本語は色々なスピーチスタイルがあることは知っていますね。

Thank you!

Answer 1

I think there are two ways to parse this:

日本語は［色々なスピーチスタイルがあること］は知っていますね。

and

［日本語は色々なスピーチスタイルがあること］は知っていますね。

In the first parsing, the second は is contrastive, as in "With respect to Japanese, you at least know that there are a number of different speech styles, yeah?"

In the second parsing, the first は is contrastive, as in "You know that Japanese has a number of different speech styles, but another language does not, right?"

There are two rules that I have internalized:

• Any embedded はs are contrastive
• The first non-embedded は is a normal topic marker, any following non-embedded はs are contrastive

I have had other people disagree with this though, so a native speaker's opinion regarding this answer is needed.