How we cite our quotes:
"At any rate, it is safer to leave people to their own devices on such subjects. Everybody likes to go their own way – to choose their own time and manner of devotion. The obligation of attendance, the formality, the restraint, the length of time – altogether it is a formidable thing, and what nobody likes." (9.15)
Though Mary is commenting on church services and how boring they are, she's also expressing an interesting philosophy of tolerance. Mary believes in letting people do their own thing, whatever that may be. This greatly contrasts with Edmund and Fanny, who each have much stricter senses of how people should behave.
"I speak what appears to me the general opinion; and where an opinion is general, it is usually correct." (11.24)
Mary is being witty, but her thoughts on the "general opinion" are revealing. Mary doesn't see anything wrong with society at large and seems happy to belong to the majority – the popular crowd and popular morality, in other words.
"Don't imagine that nobody in this house can see or judge but yourself. Don't act yourself, if you do not like it, but don't expect to govern everybody else." (13.32)
Tom scolds Edmund here for trying to boss everyone around. Edmund wants everyone to respect his (moral) authority. Tom, like Mary, embraces a much more open moral philosophy that lets people judge for themselves and do what they want.