隨著人工智慧工具與替代性資訊來源快速發展，線上社群面臨使用者參與下降與知識貢獻減少的挑戰。為了解釋使用者為何持續參與並貢獻知識，本研究結合需求—可供性—功能觀點與三構面承諾理論，探討平台層級可供性如何透過社群承諾影響線上社群中的使用者參與。本研究聚焦於兩種平台層級可供性：知識搜尋有效性與知識發文輔助，並將社群承諾區分為情感承諾、持續承諾與規範承諾，以進一步檢視其對持續參與與知識貢獻的影響。本研究採用兩波段線上問卷設計，以降低共同方法偏誤。最終取得 652 份有效樣本，並採用結構方程模型進行假說檢定。研究結果顯示，知識發文輔助對情感承諾、持續承諾與規範承諾皆具有顯著正向影響，表示平台若能降低發文與知識分享的負擔，將有助於培養使用者對社群的心理連結。相反地，知識搜尋有效性對情感承諾與規範承諾呈現顯著負向影響，且對持續承諾不顯著。補充訪談結果顯示，當使用者能快速找到所需答案時，往往傾向於將社群視為工具性資訊來源，而非需要長期投入的社群空間。整體而言，本研究指出平台功能不僅影響使用者行為，也會透過不同心理承諾機制形塑社群參與，進而補充線上社群永續經營與平台設計相關理論。;As artificial intelligence tools and alternative information sources become increasingly accessible， online communities face growing challenges in sustaining user participation and knowledge contribution. To explain why users continue to participate in and contribute to online communities， this study integrates the Needs–Affordances–Features perspective with the three-component commitment framework. Specifically， this study examines how platform-level affordances influence users’ continued participation and knowledge contribution through three dimensions of community commitment: affective commitment， continuance commitment， and normative commitment. Two platform-level affordances are examined in this study: knowledge search effectivity and knowledge posting assistance. Knowledge search effectivity refers to the extent to which an online community enables users to efficiently locate relevant and useful knowledge， whereas knowledge posting assistance refers to the extent to which an online community supports users in composing， organizing， and contributing knowledge. This study employed a two-wave online survey design to reduce potential common method bias. After data screening， 652 valid responses were retained for analysis. Structural equation modeling was used to test the proposed research model. The results show that knowledge posting assistance has significant positive effects on affective commitment， continuance commitment， and normative commitment， indicating that platform support for content creation and knowledge sharing can strengthen users’ psychological attachment， perceived dependence， and sense of obligation toward the community. In contrast， knowledge search effectivity has significant negative effects on affective and normative commitment， while its effect on continuance commitment is not significant. Supplementary qualitative interviews suggest that when users can quickly obtain the information they need， they may treat the community as an instrumental tool rather than as a social space requiring sustained involvement. Furthermore， all three dimensions of community commitment positively influence continued participation and knowledge contribution， and continued participation further promotes knowledge contribution. Overall， this study demonstrates that platform-level affordances shape user engagement not only through functional support but also through distinct psychological commitment mechanisms. These findings contribute to the literature on online communities， platform affordances， and commitment by highlighting the heterogeneous effects of platform design on sustained community engagement.
