Kenya became independent in 1963.I was born in Kenya in 1956 to British born parents...
As she was born in a British colony (and because of the language of Kenya's constitution and nationality law, she did not become a Kenyan citizen at independence), she was born and remained a CUKC otherwise than by descent. The reason that she was being classified as a British citizen by descent (and the point in dispute in that thread) was because the Home Office argued that her RoA was by descent.
To be a British citizen otherwise than by descent at commencement of the BNA 1981 on 1st January 1983, the person needed to have held both CUKC otherwise than by descent AND RoA otherwise than by descent.
Either one of them being by descent would make the resultant British citizenship a citizenship by descent.
Your father, on the other hand, held both CUKC and RoA by descent (I believe that the caseworker is wrong in ascribing your father RoA through Section 2(i)(d), but that is by the bye).
Even if the caseworker ascribes your father RoA through Section 2(i)(d), as in the case of the lady in the link you provided earlier, he would still not have CUKC status otherwise than by descent and thus would still be a British citizen by descent.Section 14 of the BNA 1981 wrote:14 Meaning of British citizen (by descent).
(1)For the purposes of this Act a British citizen is a British citizen “by descent” if and only if—
...
(b)subject to subsection (2), he is a person born outside the United Kingdom before commencement who became a British citizen at commencement and immediately before commencement—
(i)was a citizen of the United Kingdom and Colonies by virtue of section 5 of the 1948 Act (citizenship by descent); or...
You have two possible courses of action;
(a) Write to the caseworker with a link to the other forum arguing that as they have attributed RoA to your father under Section 2(i)(d) of the Immigration Act 1971, that makes your father a British citizen otherwise than by descent and you a British citizen by descent.
Keep in mind though that an incorrectly issued British passport (or CoE-RoA) does not make you a British citizen and that if somebody were to review your case later on, you can be refused a British passport or CoE-RoA on renewal (as has happened recently with the British passports of some children of EEA citizens).
(b) Write to the lady on the other forum, requesting her for the contact details of her lawyer and present your case to them.