I will let you know about her response.  I know Rory McDonell is researching using essential oils, especially thyme, spearmint, and clove as slug and snail repellents.  I have not seen any published research or know of any studies being conducted about using a coffee/water solution.  I can't tell clients coming into our Plant Clinic about the coffee solution unless I have research-based information.

Hi, Kristena--I remember seeing your name a lot when I was fielding questions on Ask An Expert.  After they switched to the new platform back in the early 20s, it wasn't supported well here, and it just petered out.  Too bad--I really enjoyed the question wrangling, especially the plant ID questions.  Thank you for your response.  I hope I hear from Linda, and I'll let you know what she says.

Yes, that's the article I saw years ago.  As far as I know, it's just an article discussing some initial inquiries and short experiments. That's how the scientific process begins.  I don't think they ever pursued it.  It's a darned shame--it would have been such a simple solution to slugs in our gardens.