Hawaiian fonts getting messed up
I maintain a Wordpress site as a favor to a small Hawaiian non-profit organization whose work I support. I use the Mac font set to generate the two special diacritical marks needed to write Hawaiian words: the ʻokina and the kahakō. Those marks on the site (malamahalawa.org) get utterly messed up every time there is a Wordpress update.
This is a question for the Wordpress support forum, of course, but I have posted it there and so far, there has been no resolution: https://wordpress.org/support/topic/wp-update-totally-messed-up-my-site-again/
One response there suggested that the Hawaiian language diacritical marks generated by my OSX system do not conform to UTF-8 standard character codes, and are thus not compatible with Wordpress. This does not sound plausible to me. French, German and Spanish special characters all apparently survive Wordpress updates. What would be different about Hawaiian diacritical marks?
Does anyone here know enough about Mac character sets to help me out? Iʻd like to rule out the character sets as a possible source of the problem. Thanks!