Mentoring "inside" the action of teaching, when students are present (e.g., co-teaching, demonstration teaching), helps new teachers understand, experience, and take up complex instructional activities. Yet, studies show that mentors largely avoid inside practices, preferring to employ outside practices that occur when students are not present (e.g., debriefing, co-planning). Researchers speculate that mentors avoid inside practices because they deviate from educational cultural norms. This qualitative study uses the framework of socialized niceness to examine the cases of two experienced mentors -- one used and one avoided inside practices. Findings reveal their decision-making related to how they navigated (dis)comfort particularly around teacher authority, leveraging expertise, risk taking, and imposition -- all manifestations of socialized niceness. Niceness seeks to maintain comfort and the extent to which mentors intentionally navigate discomfort has consequences for teaching and learning. Recommendations are provided to support mentors and to expand the practices mentors employ to support new teacher learning.