HM access: unlocked or conditional?

I have a slew of pve characters, all of whom have completed both Prophecies and Factions. However, real life began to intervene after the release if Nightfall, and as a result I have only beaten it with one character.

My question is this: can I safely reroll that character without losing the ability to play NF in hard mode with other characters? Essentially it's a matter of whether HM is treated as an account-wide unlock or tied to a specific character.

The second sentence is just ambiguous enough not to provide a solid answer.

I deleted my warrior, who was my only character who had beaten prophecies, and I had to beat it again with my ranger to have access to HM.

to go in to hardmode, you must have protector title for that continent (have beaten all missions with bonus/masters)

All I think you need is to have beaten the final mission for whatever campaign.

That is wrong.

You only have to beat the game with one character and then log into that character once.

As for the original question, I have no idea. If you're close enough to the end I'd just go ahead and reroll.