How does Infect interact with Lifelink?

Question

When a creature with Infect and Lifelink puts poison counters on a player, does the controlling player gain life? Do all abilities that trigger on combat damage still occur?

A link to an official ruling would be helpful.

Answer 1

Yes, the creature's controller will gain life.

Infect and Lifelink are both abilities that modify how damage is dealt. They're not exclusive in any way; they just mean that the damage dealt has some effects different to what damage normally does. They can happily coexist.

119.3b Damage dealt to a player by a source with infect causes that player to get that many poison counters.
...
119.3f Damage dealt by a source with lifelink causes that source's controller to gain that much life, in addition to the damage's other results.

The damage is still damage in every way. So it'll still trigger an Ophidian Eye, get doubled by Furnace of Rath, get prevented by Samite Healer and so on.

The Scars of Mirrodin FAQ document says:

Damage from a source with infect is damage in all respects. If the source with infect also has lifelink, damage dealt by that source also causes its controller to gain that much life. Damage from a source with infect can be prevented or redirected. Abilities that trigger on damage being dealt will trigger if a source with infect deals damage, if appropriate.

Answer 2

Creatures with Infect still deal damage, so all abilities that trigger* (such as Lifelink) still function.

This is a natural consequence of rule 119.3b and 119.3d (and others, like 702.87x, omitted here)

Damage dealt to a player by a source with infect causes that player to get that many poison counters.

and

Damage dealt to a creature by a source with wither and/or infect causes that many -1/-1 counters to be put on that creature.

(Source)

Note that both Infect and Lifelink occur as a consequence of damage being dealt, thus it follows that any other damage triggered* ability would also occur.

_{*As AlexC points out, the actually phrase "trigger" can be tricky. Think "caused to happen, through any of MTG's myriad rules."}

Answer 3

Yes to both. The FAQ for Scars of Mirrodin states that creatures with infect deal damage to players in the form of poison counters; that's still dealing damage, so lifelink and other abilities that trigger on combat damage take place as normal.