FAVoR: Measuring and Mitigating Author-Style Homogenization in Federated Personalized Generation

Lu Han, Jingyao Zhang, Katy Ilonka Gero, Nguyen H. Tran


Abstract
Large language models are increasingly used as personalized writing assistants, but adapting a model across many authors can compromise individual writing style by pulling author-specific signals toward a shared register. Federated parameter-efficient fine-tuning (PEFT) offers a data-local setting for this multi-author adaptation problem: clients keep author text local while sharing compact adapter updates. However, we show that standard aggregation can preserve continuation utility while making different authors’ generations less distinguishable in style space, a failure mode we define as author-style homogenization. We evaluate author-style retention with Angular Style Classification Encoder (ASCE)-based diagnostics on our main BlogText benchmark and ASCE-independent external authorship verification. Using this protocol, we find that common federated PEFT baselines can preserve semantic utility while averaging out author-specific signals. To address this homogenization, we instantiate FAVoR (Federated Authorial Voice Retention), an author-style residual mechanism for federated PEFT. FAVoR uses a shared-private adapter design: clients upload shared-adapter updates while retaining author-specific residual corrections locally. Across BlogText and external Mythos-Reddit validation, FAVoR improves author-style retention over standard and personalized federated PEFT baselines. These gains come with small continuation-utility trade-offs and are supported by component ablations, external verification, and cold-start transfer.
Anthology ID:
2026.emnlp-main.365
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
8359–8384
Language:
URL:
https://aclanthology.org/2026.emnlp-main.365/
DOI:
Bibkey:
Cite (ACL):
Lu Han, Jingyao Zhang, Katy Ilonka Gero, and Nguyen H. Tran. 2026. FAVoR: Measuring and Mitigating Author-Style Homogenization in Federated Personalized Generation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 8359–8384, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
FAVoR: Measuring and Mitigating Author-Style Homogenization in Federated Personalized Generation (Han et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.365.pdf