Thanks for your kind comment. Fever is one of the most common symptoms of Covid. Covid can cause symptoms other than the three I focused on. So I may have oversimplified Covid in the article.

Notably, sign is actually the better choice of word for fever. Sign is an objective manifestation of the disease (e.g., fever, pink eye), whereas symptom is a subjective manifestation (e.g., fatigue, headache). I stick to symptoms as I think that's what most would understand.

So, fever was an actual sign of Covid or, more specifically, as you've said, an indication of your immune system battling Covid. Anyway, I'm glad you have recovered from your previous bout of Covid, without any long-covid, I hope.