This FAQ explains that S2 journals display comments in GMT. However that is not always the case. If the user has set their journal to S2 but is using 'old-style comment pages' then comments in their S2 journal will display using S1 time.
Should the FAQ be updated something like:
"The timestamps on comments in journals using S2 display using the GMT timezone unless old-style comment pages is selected when the comments will display with S1 timestamps."