I don't think this is a grey zone at all. Senior professionals in all domains, not just acadaemia, routinely sign letters that they did not pen:
- Directors signing press releases written by communications managers
- Vice-chancellors signing letters to government officials written by deputy vice chancellors
- Academics submitting journal articles that were written by a co-author, although the research is shared.
It's completely irrelevant who actually put the words together, unless there is a question over the copyright of the text - which there clearly isn't here. All that matters is that the person signing the letter stands by its content and takes responsibility for it.
If you write a reference letter for yourself that is over the top, they won't sign it. No ethical issues here whatsoever.
(I can't answer whether other institutions would frown on the practice for other reasons though.)
Ok, some research.
Guidance from p. 3 of "Writing a Letter of Recommendation" (an addendum to Making the Right Moves, published by the Howard Hughes Medical Institute and Burroughs Wellcome Fund):
Tip: Don’t ask the candidate to write a draft of the letter for you. Most heads of labs say this rarely saves time and sometimes leads to a weaker letter. It is better for the candidate to provide you with all the necessary information, from which you can then pick and choose as you write your letter.
...and from p. 9, guidance for the applicant:
You may be asked to write a draft of the letter. As mentioned on page 1, many heads of laboratories say this is not a good idea. However, if you are asked to do it, do it!
From "Letter of Recommendation: Writing One Yourself" on the Peterson's website:
When requesting a letter of recommendation, don't be surprised if your instructor or supervisor hands the forms back to you and says, "Sure, why don't you go ahead and write the first draft yourself, and I'll revise it and sign at the bottom."
From "Writing Your Own Letter of Recommendation" on StudentBranding.com:
- The “draft” that you provide to the recommender to sign shouldn’t be a draft at all – it should be a perfectly polished letter ready to be signed, sealed and delivered.
- Don’t be insulted when your supervisor decides to edit. They’ll want to apply their own language and voice to your content.
[...]
In my experience as a supervisor . . .
I’ve been asked to write lots of letters of recommendations for students, but I’ve never felt strongly enough to throw the responsibility back at someone. That’s not to say I haven’t managed some phenomenal students; I just haven’t had someone come along who I think is up to the task. So, when he or she does come along, that person will really be top notch.
From "How to Write Your Own Recommendation Letter" on Firsthand.co:
[...] While the standard practice is for references to write their own recommendation letters, it’s becoming increasingly common for time-strapped individuals to ask you to pen the first draft of a letter yourself. [...]
From "Is it OK to Write My Own Letter of Recommendation?" in BusinessMajors.About.com's Recommendation Letter FAQ:
Question: Is it OK to Write My Own Letter of Recommendation?
Answer: The only time it is acceptable to write your own letter of recommendation is when the person you requested the letter from asks you to do it. Even then, it is important to be honest in the letter. Don't write anything the other person wouldn't have written. When you have finished, ask the person to look over the letter, verify the information, and sign. You should never forge someone else's signature.
I don't see much (any) evidence of any ethical quandaries in a professor requesting and submitting a letter of recommendation directly from the student. These examples aren't cherry-picked - they're the first few hits that came up when searching for phrases like "own letter of recommendation" or "letter of recommendation myself".
In summary:
Is it acceptable to write most of the reference letter and have the prof make minor edits?
Clearly, yes - if requested to do so.
Do academic institutions frown upon this practice?
No.
Would it be considered an academic offense if a student wrote a reference letter for themselves and had a prof sign it?
Hell no.