Upgrading armor

If one had 2 articles of armor, One with a rune of say, (A, "the grove"), and one with say, (B, the rune of "Rata Sum"), and you upgraded one of the armors, A, with a "Rata Sum rune", to make two Rata Sum armors, what would be the result. 1) The "grove rune" or both blows up and disappears, loosing the both armors ) The "Grove rune" turns into a "Rata Sum rune", 3) or nothing at all, or maybe something else. Which one fellas?

the new rata sum rune will destroy and replace the gtove rune and you will have 2 out of 2 bonus for the rata sum runes.

Adding a rune to armour, even overwriting an existing one, will never destroy the armour.

If you add a new rune without removing the old one you will lose the old rune but keep the armour and the new rune.

There are items which can remove runes or other upgrades but they're expensive or hard to get so only really worth using for valuable runes.

Replacing a rune in gear that already has a rune in it will only overwrite the rune it had. Hence, the "Rune of the Grove" will be destroyed and replaced with "Rune of Rata Sum". But yes, as some also said, since you have two pieces of armor with "Rune of Rata Sum", you will now get the two-rune bonus.

The same thing can be applied for sigils, however: two of the same sigil type will not benefit each other. Only runes work in tandem. But the overwriting is the same: only the old sigil gets destroyed.

Excellent, thank you all! =)