One way to find out whether we have had a thread on something is to start a thread on it and then wait for the OP Tipping, OP Tipping, OP Tipping…
I should probably ask, “Which set of letters forms the biggest set of words that, mutually, are anagrams?”, or some such formulation but you know what I mean.
Common answer seems to be “retains”, though the number of anagrams depends on the wordlist.
The following should not be controversial
The OED also lists eranist meaning a club member. Not sure whether that is current.
OED also gives ratine, as an acceptable form of ratiné, a kind of fabric “or a piece of this”. Given that it doesn’t say “plural same” I suppose we assume that ratines is an English word.
That gets us to 12 without too much fuss.
Now, anagrammy.com also lists asterin and sainter.
I am seriously dubious about the latter. Saint can be an adjective, and also a verb, which might lead a bot to think that sainter could be a word, but when you consider the meaning of that adjective and verb ... no.
Is asterin a word? It does not have an entry in the OED, but it DOES appear in the references for the OED entry on purple-red
1934 C. C. Steele Introd. Plant Biochem. vi. xix. 219, 3-Glucoside: Chrysanthemin in red varieties of Chrysanthemum indicum and asterin in the purple-red Aster (along with callistephin) are identical.
This page on medicinal plants mentions it:
“- A glucoside, chrysanthemin, an isomer of asterin”
This old report from the Agricultural Experiment Station of Oregon State University also lists asterin as an alternative name for chrysanthemin. This was published in May 1993.
So I think we can allow it. That would get us to 13.
Can that be topped?