E-mail address "overlay" with "drag & drop"

Question

The following errors occurs doing a "drag & drop" from the Address Book or using the "Contacts Sidebar". Unless you "drop" at the end of the line, sometimes it "drops" exactly where the cursor was (because sometimes I see a red cursor and sometimes I don't so have no idea of exactly where it will place it) "overlaying" the e-mail addresses on the line (but sometimes, it put each one of the e-mail addresses on a new line). Either append them to the end of the line or on separate new lines or don't allow the "drop" but please don't "overlay" ("insert" between) whatever is already there!
Also, when I tested "dropping" multiple e-mail addresses from the Address Book, a comma was NOT inserted between the multiple e-mail addresses thus making the entire line of e-mail addresses "invalid". And, it suffers from the identical "overlay" problem described above.
If you have any difficulty understanding the problem, I will gladly provide you anything you need. Just ask.

Answer 1

It appears that the add buttons always copies each E-mail address to a new line so it does not suffer from the lack of comma separators or "overlaying" existing E-mail addresses.
However, that doesn't eliminate the two defects unless Thunderbird disables the "drag & drop" of E-mail addresses which are popular on other E-mail clients. In fact, that is how I noticed the problem: assisting someone with migrating to Thunderbird from another obsolete E-mail client. He is extremely reluctant to giveup his old way of doing things which was "drag & drop" from the Address Book but I am trying to get him to change.