Does Doubling Season affect loyalty counters placed on a planeswalker as it enters the battlefield?

Doubling Season's counter-doubling effect applies when an effect would place one or more counters on a permanent you control. However, a planeswalker doesn't enter with loyalty counters placed on it by a spell or effect — it enters with loyalty counters as a defining characteristic of the card itself, set by a replacement effect.

CR 614.1c establishes that a planeswalker's loyalty entry is handled by a replacement effect: instead of entering with no counters, it enters with loyalty counters equal to its printed loyalty. This is not an "effect placing counters" in the sense Doubling Season modifies — it is a self-replacement effect intrinsic to the planeswalker (CR 306.5b).

Doubling Season (and similarly Parallel Lives) uses the wording "if an effect would place one or more counters on a permanent." Because the loyalty counters are placed by the planeswalker's own replacement effect rather than a separate effect, Doubling Season's replacement effect does not apply (CR 614.5 governs how replacement effects interact, and only one applies here — the planeswalker's own).

This was officially clarified and is consistent with tournament rulings: Doubling Season does not double the starting loyalty of a planeswalker entering the battlefield.

Example: You control Doubling Season and cast Jace, the Mind Sculptor (starting loyalty 3). Jace enters with exactly 3 loyalty counters, not 6, because his loyalty counters come from his own replacement effect, not from a separate effect that Doubling Season can intercept.