ran into this question, and wanted clarification if this should be considered off-topic or on topic.
It seems to me like it is in a bit of a gray area, but could be rephrased to be on topic as the gist of the question could be rewritten as follows:
How useful is anime / managa for learning conversational Japanese?
Which I feel would be a valid question since we can likely have some valid targeted responses to the question. Additionally, it should be a one-off question that doesn't need to be repeated where as a question along the lines of:
Is [name] a good [anime / managa] for learning Japanese?
Is a pattern that could come up many times.
It's not about the language itself, so IMO it's off-topic.