Just on your point with "Is there any indication in written french when a silent T should be pronounced?", with elision you will pronounce a consonant sound (including T) before a vowel sound (je suiS_allé; leS_hommes).

In the reflexive, "ils/elles" forms *always* end in a T, and since both "ils" and "elles" forms start with a vowel, this means that inversion will *always* result in a pronounced T sound.

croienT_ils [qqch]? l'onT_elles fait? ne l'avaienT_ils pas vu?

Adding a T to create this effect is only necessary with the il/elle/on form in the present tense, because that is the form that usually ends in a vowel, and il/elle/on all begin with a vowel: hence, the problem of two ugly vowels colliding with each other. These problems don't exist with the other forms because the following pronoun is not a vowel (begins with j/t/v/n) except for ils/elles, which always has that t in the verb anyway.

Mark - this may help.

https://www.frenchtoday.com/blog/french-grammar/inversion-in-french/

Thanks.. that is useful although not entirely sure about Où habite-t-elle ?.. rather thought that was pronounced anyway!