I've had a look at the Act - it"s available on the Legislation.gov website.
There's a section on the meaning of the characteristics - the following are relevant here:
"(7)A person is a member of a group defined by reference to transgender identity if the person is—
(a)a female-to-male transgender person,
(b)a male-to-female transgender person,
(c)a non-binary person,
(d)a person who cross-dresses,
and references to transgender identity are to be construed accordingly.
(8)A person is a member of a group defined by reference to variations in sex characteristics if the person is born with physical and biological sex characteristics which, taken as a whole, are neither—
(a)those typically associated with males, nor
(b)those typically associated with females,
and references to variations in sex characteristics are to be construed accordingly."
I take it that saying Caster Semenya ir someone similar is a male might get caught under this section. It's evidently shaped by the forced teaming of "intersex" with the rest of the letters.
However, it:s worth reading the part on "Protection of freedom of expression, particularly the word "solely":
"9 Protection of freedom of expression
For the purposes of section 4(2), behaviour or material is not to be taken to be threatening or abusive solely on the basis that it involves or includes—
(a)discussion or criticism of matters relating to—
(i)age,
(ii)disability,
(iii)sexual orientation,
(iv)transgender identity,
(v)variations in sex characteristics,
(b)discussion or criticism relating to, or expressions of antipathy, dislike, ridicule or insult towards—
(i)religion, whether religions generally or a particular religion,
(ii)religious beliefs or practices, whether religious beliefs or practices generally or a particular religious belief or practice,
(iii)the position of not holding religious beliefs, whether religious beliefs generally or a particular religious belief,
(c)proselytising, or
(d)urging of persons to cease practising their religions."
Finding/creating a network of useful lawyers would be good, too.