Reddit has become a "trust signal source" for AI search as an extension of Google's "content quality first" strategy with LLM providers from 2025-2026, with Google's 2025 update to the "helpful content algorithm" prioritizing "real user discussions" from Reddit and Stack Overflow, while AI systems like ChatGPT and Perplexity adopt Reddit as a "high signal data source," creating a feedback loop of "Reddit mentions → AI citations → search rankings." This parallels the rise and fall of "SEO link farms" in 2023-2024, where brands bought backlinks until Google's "spam content update" in 2024 targeted them; the 2026 "Reddit AEO" shifts from "manipulating backlinks" to "manipulating community mentions," but platforms like Reddit and algorithms from Google/AI may jointly crack down, causing the "manipulation dividend" to disappear. Brands pursue a dual-track strategy of "organic mentions + paid promotion," using AMAs, real user reviews, community engagement, Reddit Ads, KOL collaborations, and Subreddit sponsorships, but the boundary between "organic" and "paid" is blurred—when employees pose as real users, it constitutes "manipulation," hard for moderators and algorithms to distinguish. This reflects a "search paradigm shift" from "keyword matching" to "community trust signals," as AI systems need "real human experiences