I saw some moderators deleted a some few comments about God and Islam which were not long discussions. I remember SE says only long discussions are not welcomed and can be moved to chat. and SE itself warns when comments become long.
are mods allowed to delete anything based on their personal prefers? or when they delete they should refer to some link explaining the reason of delete?
In the case of this question: What is fundamentally unique about Islam? the reason for deletion was the non-constructive argumentation of the other user. His comments did not directly engage your answer and were only meant to bait an argument on a tangentially related topic. Also the tone and language were quite offensive. Given all these, I think it was perfectly alright to delete those comments. It's not the length of the discussion per se, it's whether or not it was appropriate.
SE sites are generally Q&A sites, not discussion sites, any form of discussion and debate is discouraged. Discussion, debate, and arguing are generally not welcome.
Comments are not meant for discussions/arguing/providing an alternative perspective. The comments are meant for things like suggestions for improvement, asking clarification about the question, and pointing out problems with an answer.
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