Are Players a Source They Control?

[AnotherAlias]

If I, as the player, deal damage to a target, using Abian, Luvion Usurper (-X ability), would that trigger City on Fire?

[WizardMN]

This is the rule for sources of abilities:

113.7. The source of an ability is the object that generated it. The source of an activated ability on the stack is the object whose ability was activated. The source of a triggered ability (other than a delayed triggered ability) on the stack, or one that has triggered and is waiting to be put on the stack, is the object whose ability triggered. To determine the source of a delayed triggered ability, see rules 603.7d-f.

And the definition of an object:

109.1. An object is an ability on the stack, a card, a copy of a card, a token, a spell, a permanent, or an emblem.

So, strictly speaking, players are not objects which means they are not sources. However, you are asking about a card that doesn't exist within the rules (Acorn, Silver Bordered, and Playtest cards exist the way the do primarily because they don't work within the rules) so you are free to interpret the rules however you want when dealing with cards like Abian that don't adhere to the rules anyway.

Also, City on Fire is not a trigger. It is a replacement effect.

[void_nothing]

While WizardMN correctly notes that Abian and other playtest sticker cards fall into the same category as silver-bordered, acorn, and Heroes of the Realm cards as being outside the scope of the Comprehensive Rules, I will say that rule 719 (controlling another player) and particularly rule 719.9 suggest that players do in fact control themselves. This is highly unofficial and only my interpretation, but it does have an analogy in real rules.