French language Q&A Forum

Am I right in thinking that "me" is used indirectly here as there is no agreement with the past participle of dire (dit/e) 

Firstly - thanks to the creators of this lesson!

Secondly - I am having trouble understanding the distinction between the usage of "Manquer de..." and the impersonal "Il manque...à..."

The lesson describes how the two structures are formed (and gives translations that seem to overlap - e.g. "to lack [something]" VS. [someone/something] is missing (i.e. lacking) something), but doesn't seem to describe how exactly they are used differently from each other.

Thus, I'm wondering if someone can explain in what scenarios "Manquer de" must be used and not "Il manque...à..." (and vice versa), and describe if there are any situations in which both can be used.

(For an example of what I mean, can one say both "Il manque un bouton à ta chemise" (given in the lesson) and "Ta chemise manque d'un bouton" ? Why or why not? Etc.)

Thanks in advance!