What Becomes Visible About University Sustainability Online? A Pilot Lexicon-Based Analysis of Public Discourse and Its Validity Limits

This pilot study examines what becomes visible about university sustainability in public online discourse. From 14,621 harvested records, a sentence-level screen retained 536 posts and comments (Reddit, Hacker News and Lemmy; 2007–2026), coded with documented lexicons for strategy, curriculum, pedagogy, campus operations, community engagement, reporting and promotional communication. Instead of human inter-coder reliability, a blinded, AI-assisted semantic second pass by a different model family under a frozen prompt served as a provisional cross-method check on 236 retained units and 120 excluded records. The second pass judged 153 of 236 retained units as relevant. Campus operations was the most frequent domain in both methods (lexicon: 70.9% overall; second pass: 53.6%), but its lead depended on operational search terms; the second pass placed engagement (41.8%) ahead of curriculum (36.6%), indicating that the lexicon undercounted engagement. Cross-method concordance was substantial for curriculum and operations (κ = 0.67; 0.64) and weak for interpretive codes. Explicit SDG naming was rare (1.3%). Claims co-occurred with evidence more often than chance (OR = 3.10), being robust to length adjustment and a null permutation. The association between promotional communication and asserted claim–practice gaps remained undetermined, as 8 of 120 sampled excluded records were judged relevant, and 29 Global South communities searched in English yielded one unit. A provisional single-axis scheme grading the co-occurrence of claims, practice references and evidence (L0–L4) was not stable across methods (weighted κ = 0.13). This study documents what such evidence can and cannot support pending human validation.