It appears any gem tags that apply to either the regular or vaal version get mixed together and displayed on a single line. Does this mean they actually inherit tags from each other? I guess the two skills come from one item so they share a level requirement which only gets displayed on the regular version. By that logic they share tags as well. If you need poe orbs cheap in game, you can choose u4gm.com sale cheap poe currency.

Let's say I'm using the new Purity of Fire/Lighting and the vaal version has a powerful duration effect I want to lengthen. Will Increased Duration raise the mana reservation of the regular version and lengthen the vaal version? Vaal Righteous Fire now has a duration burn which would give normal Righteous Fire the duration tag. Can it be supported by Swift Affliction and Less Duration without doing the Arcane Surge workaround? If regular skills inherit the vaal tag can they benefit from items that modify vaal skills?

Supports don't actually care about tags. Vaal Impurity of Fire would get bonus levels from "+1 to level of socketed Duration gems" and that would affect the level of Purity of Fire gained from the gem as a result. That doesn't make the regular purity of fire a duration skill, which is what Increased Duration Support looks for.

Tags are just for the purpose of modifiers like "+ to level of fire gems", that's almost the only thing they're used for. Supports don't look at gem tags at all, they only look at "supportability" which isn't a category that is displayed. Eg, Burning Arrow is not a Duration skill, tag-wise, but it is supportable by Less Duration because of its threshold jewel that creates burning/tar ground.

But, Vaal Burning Arrow gem has the "AoE" tag, so if you put it in a "+ to level of AoE gems" item, then both the vaal version and the normal version should get + level, because the gem does have the tag that the modifier is looking for.