Dr. Fawthrop wrote:I [...] expect them to address me as Dr. Fawthrop. Many of them do, but some will call me Mr. Fawthrop.
If someone called himself "go teacher", I'd assume it is because he is teaching go, not because he wants to adorn himself with false laurels implied by the term "teacher".
And even supposing the person in question is fluent in Japanese cultural etiquette regarding the term "sensei", one could still argue that his target audience likely is not. Therefore, as the person has already been revealed to be aiming at an anglophone market, I don't see much point in discussing the "true" connotations carried by the Japanese word "sensei".
When I heard someone in my go-club refer to someone else (also in the club) as his "sensei", I thought it was a bit weird, but the idea was simply that of indicating some form of teacher-student relationship between the two, however casual. I believe I've observed similar usage on KGS.
Loanwords don't necessarily mean what they meant in the original language.
As an example, Germans say "handy" (English pronunciation) to mean "mobile phone".
A borderline topical quote to finish:
James Nicoll wrote:The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary.