The example sentence in Why is も used instead of が in the
sentence 「日本ではクモを見ると良いことがあると言う人もいますよ」, got me thinking "Why is
it using で, not に?". I.e., why not It seems obvious that 日本では is
intended to modify います. If it were modifying 言う, the meaning
would be roughly "There are people who - when in Japan - say
that ...". Although I would personally use に in this sentence,
it doesn't sound completely ungrammatical to me as it is. So why
is that, given that いる usually takes に, not で?