***** NOT A TEACHER *****
Good morning, Enydia.
(1) I have checked my dictionaries & books:
(a) In respect of, in respect to, with respect to, respecting = all "good" English. They can usually be used interchangeably.
(b) My two good dictionaries had "with respect to" > referring to, concerning, with reference to. (they did not list "in respect to")
(c) Dr. Randolph Quirk's famous grammar book gives many combinations:
with reference to
in/with respect to (He apparently agrees that they are the same)
On the matter of
With reference to
In respect of
(d) One business English textbook suggests:
in regard to/ with regard to
(e) In a business letter, sometimes people just write:
Re: invoice 87 (re = in re > regarding)
Some experts say that "re" is being replaced by "subject."
(2) As you already know, these terms are very formal and used in business
letters. If you wrote "With respect to" to your family or friends, it might
mean that you are angry with them!
Have a nice day!
Student or Learner