“A rachmanus” is often used to mean “a situation which evokes feelings of pity.” For example, “Beryl is such a rachmanus” would mean that something about Beryl’s personal situation induces one to feel pity towards him.
Why would one need to have pity on Chazal over their machlokes? Machlokes leshaim shomayim is not machlokes like what people try to avoid in our times. Chazal were trying to clarify Emes. That is the purest kind of machlokes.
Please explain further what you mean, as I must not have understood what you were trying to ask.