This paper reports a dialectal split in syllable-final nasal mergers between northern and southern Taiwan Mandarin: both /in/ → [iŋ] and /əŋ/ → [ən] are found in northerners' speech, while an additional /iŋ/ → [in] is reported among southerners. The former two mergers are treated as innovations while the latter is due to negative Min transfer. Rule connotation seems to be a combined result of origin, analogy, and speaker confidence. /iŋ/ → [in] is stigmatized due to Min transfer, /əŋ/ → [ən] has acquired a slight negative tang by analogy, and /in/ → [iŋ] is deemed as fairly positive. Regardless of rules, northerners, being speakers of the standard dialect, are generally more receptive to merged forms than southerners. A positive correlation is found between rule connotation and development. /in/ → [iŋ] is the closest to complete phonologization, followed by /əŋ/ → [ən], and /iŋ/ → [in], which is the least developed. Rule interaction is found in speakers that have both rules involving /i/. Those who have only one rule show higher merging rates than those who have both rules. Conflict of social connotation and increased cognitive loading are posited to be the cause.