I agree wholeheartedly with what you've said because most of the posts I've read have put Ianto as the victim with Jack as the aggressor which is something I haven't seen.

I think the flirt distraction was something Jack picked up before being partnered with John, I'm sure he knew he was a turn-on for many many 'people'.

I think the problem with their relationship most likely stems from the fact the writers weren't writing a Janto ship in S1 because Ianto was meant to be just in background to be killed off either a) during Cyberwomen b) at the end of the season. Season 2 we've had the whole relationship thrust into our faces not just the sex but everything, Jack telling Ianto he loved him, the whole scene during Adam when he knows instantly something is wrong and figures it out as well as giving Ianto support, Jack's excitement at going weevil hunting with Ianto, both of them stood in the cinema with Ianto explaining what he saw and Jack's just looking at him rather then the screen also add to that the scene in the boardroom when Jack explains a little of his past. All this shows more then a sexual relationship. I think its down to Ianto's closed off personality that he wants to keep this side hidden plus it doesn't damage Jack's mystic to the others.