This is a quote from Steve’s book, where he is quoting somebody else. I’ve not seen this grammar before.
I always thought より and よりも were used for comparison/“than”. For example, 僕の英語は日本語より上手です。
I’ve never seen ~の方がより before.
In the sentence from Steve’s book, my best guess at a translation is, “Form is more important than the subject.” which obviously, doesn’t sound right.
～方がより is also used for comparison/“than”. Your interpretation about that sentence sounds right to me.
“より重要だ” literally means “more important”.
"より美しい” means “more beautiful”.
“内容よりも形式の方がより重要だ” is the same as “内容よりも形式の方が重要だ”.
（The form is more important than the content.）
In Japanese, the expression “より” in “より重要” is redundant.
If you compare “昨日よりも今日の方が暑い” and “昨日よりも今日の方がより暑い”, the former is more natural.
“より” in “より暑い” is redundant. I notice a scent of “butter” or translation style there.
Thank you so much!
EDIT: Quick question: in your post you say, “The content is more important than the form.”
I thought it would be, “The form is more important than the content.” Is that not correct?
肉より~~です = ~~than meat.
Do I have it backwards?
Thank you again!
“The form is …”
You are right.
To me, より as in より重要だ just emphasizes the 重要だ. You could replace it as さらに or もっと.
This is an interesting topic.
If you say A is more important than B, you do not necessarily think that B is important.
If you say A is no more important than B, you probably think that both A and B are unimportant.
If A and B are both important and A is more important than B, you could say A is “より重要” in Japanese.