Does "в то же время" need to have commas here?

Question

Do I need to place commas right before and right after в то же время?:

Казалось бы, всё правильно, но здесь кроется очень опасная и в то же время весьма популярная сегодня мысль о том, что...

Answer 1

Short answer: no, you don't, see this article on Грамота.ру.

Long answer: Грамота.ру doesn't carry a lot of authority in the eyes of professional editors, but it can be used as a reference source with about as much trust as Wikipedia on neutral themes: you shouldn't quote it, and occasionally it can be mistaken, but generally it's an alright starting point.
I can't seem to find this in Справочник Розенталя fast enough, but the general sense is that "by default" you don't put any commas anywhere, unless stated otherwise. In this case we know that "в то же время" is not вводное сочетание, and therefore, there is no reason to surround it with commas.

Answer 2

No, never. Generally, when in doubt, don't. Hypercorrected extra commas produce a worse impression than omitted ones. You can't pin them down on carelessness.