Most of the sentences can be trivially rewritten without the use of "I", but the author still chose to use it anyways.
I have been contacting a large group of people and many
have specifically asked if you were attending.
Versus..
Many people on the contact list have specifically asked if
you are attending.
And likewise, there are sentences the "more powerful" person could have written with the word "I", but did not.
The idea of a reunion is a nice one
Versus..
I think the idea of a reunion is a nice one