"It is a very inconvenient habit of kittens" is a quote from Alice, expressing her frustration that kittens always purr regardless of what is said to them. She wishes they would purr for 'yes' and mew for 'no,' so that conversations could be clearer and more meaningful. Alice finds it difficult to communicate when the responses are always the same, making true dialogue impossible.

This remark highlights Alice's humorous observations about the odd behaviors of animals and the challenges of understanding others when their responses lack variety. It underscores her curiosity about the way things work and her desire for more straightforward and logical interactions, which are frequent themes in her adventures in Wonderland.