It would take a lot of styling to get existing html tags to do what <details> and <summary> do. Also those styles would apply only to what I see, not what everyone else sees. If I remember correctly, the style attribute, and maybe even the class attribute, has been disabled. So, how would you suggest that I get the <div> or <p> tags to act like <details> and <summary> for everyone who reads what I post? Also, <details> and <summary> are semantic whereas styled <div> or <p> tags are not.

So, sure, I could add styles to my personal css here on PerlMonks, but would those styles be copied to everyone elses' css too? Would you add those styles to your css? Would the styles even work?

I do not see how this would create a problem.