> Converting atmospheric CO2 to atmospheric methane is less bad than releasing sequestered methane into the atmosphere but still terrible.
Sure, if this conversion led to more and more methane in the atmosphere, it would be terrible. In this case, however, the overall amount of methane in the atmosphere due to rice will stay the same, since it's a cycle.
It's all about cycle length. CO2 from shallow ground cycles into the air, then it quickly cycles back into the ground. The forest burns, the forest regrows. CO2 leaves, CO2 returns.
Fossil fuels are also a cycle. We bring up the fossil fuels from deep ground and a million years later that CO2 returns to deep ground. That's a long cycle, that's a problem.
Isn't it the case that a lot of fossil fuels were biomass accumulated in a time before microorganisms had evolved to be capable of digesting woody plants and so are largely non-repeatable because the circumstances which can lead to coal are now narrower?
Sure, if this conversion led to more and more methane in the atmosphere, it would be terrible. In this case, however, the overall amount of methane in the atmosphere due to rice will stay the same, since it's a cycle.