Learn Russian: Внешность Анны интереснее внешности Ивана. - Anna's appearance is more interesting than Ivan's appearance.

In Russian, when you compare two things without using the word чем (than), the second item in the comparison takes the Genitive case. Here, интереснее внешности means 'more interesting than the appearance'.

Why does внешность change to внешности in this sentence?

Внешность (appearance) is a feminine noun ending in a soft sign (-ь). To form the Genitive case for these nouns, you replace the soft sign with -и.

Why is the word order внешность Анны instead of putting Anna's name first?

To show possession in Russian, we use the Genitive case and place the possessor after the noun it owns. So 'Anna's appearance' becomes внешность Анны (literally 'the appearance of Anna'). The same rule applies to внешности Ивана at the end of the sentence.

Does the comparative adjective интереснее change depending on the gender of the noun?

No. When you form a comparative adjective by adding -ее to the stem of the word (from интересный), it becomes a fixed form. It stays интереснее regardless of whether it describes a masculine, feminine, or plural noun.