about the last and unnecessary thank you emails:

My experience is that i sometimes get rather insulted by receiving a thank you! (especially with the exclamation sign, but also without).  The situations this happens in, are happening in my inboxes.

It goes like this

To Me: Hi, can you please send me something that you've got and I need? regards, Ben.
From me: Sure, here it is, hope it works out all right!
To me:  Thank You!  sincerely FULL NAME (as if i didn't know or what?).

And by this i get insulted.  I experience this gesture of saying unnecessarily thanks as a power statement, a way of having the important last word, a way of proving that you are the initiator who in the end of the line makes society breathe and expand to something better.  Of course this also means that I feel it is unnecessary to thank me, because i feel the thanks are already implied in the question and our relation of mutually helping colleagues.  Even if it is a slight chance it actually is the way to go about, I'm still insanely provoked by the format featuring exclamation signs and full name (not as a signature attached to all your emails!)

I DON'T WANT TO HEAR IT!  - I'm glad to help you, frankly i'm happy to help pretty much anyone (i get a borderline sick satisfaction from helping people - it makes me feel powerful - even if i simultaneously feel used).  But I do not need me helping you exercising how to manage your social situations in email-format.

I'm obviously not exercising anything but hostility towards colleagues, I'm pretty much denying every possible positive idea connected to the last and unnecessary thank you email or text message.