"Off of" is often considered ungrammatical, although whether it actually is is up for debate. See eg The Grammarphobia Blog: Is “off of” so awful? https://grammarphobia.com/blog/2009/12/is-off-of-so-awful.html It is also American focussed in use, so, as a Brit, I would always try to avoid.
Alright a few points here, mainly just digging a bit further and ceryainky not saying youre wrong. And im pretty bad with remembering parts of speech so excuse me if im incorrect here. For one, the article, written in 2007, says that it will likely be a part of standard american english in the near future, so it supports it being acceptable (in american english, which i am american.) Second, every time i see it refuted as "improper" its in a fairly simple preposition, usually with a single noun that is preceded by an article. Meanwhile, my usage uses what i believe is called a noun dependant clause(?), which does not have an article preceding it, but rather a preposition. To my ears, off of [article] sounds clunky and weird, and i would use off [article], i.e. off of a couch vs. Off a couch. However, off [preposition] sounds worse than off of [preposition], as in my former example, off of how vs. Off how (Sorry for any bad spellings, my phone screen is kinda broken lol)
As a Canadian, I would say that "off of" is so ubiquitous (at least where I'm from) that it just feels like a normal part of the language like any other combined preposition (away from, on to, outside of -- but maybe these are equally ungrammatical to some people?)
Depends what your definition of "is is" is
Always makes me wince as a Brit.
‘Off of’ is perfectly acceptable in the right context. Eg “get off of me”.
It’s “Briton”. “Brit” is American.