What does "to the prejudice of discipline" mean?
In this case:
- prejudice means "detriment; damage".
prejudice:
- [..]
- damage or injury; detriment: a law that operated to the prejudice of the majority.
- to the prejudice of: to the detriment of.
(source)
discipline means "behavior in accord with rules of conduct".
"to the prejudice of discipline" means that the discipline suffers because the newspaper office attracts all kinds of people. The next sentence from the book shows an example of this:
Zenana-mission ladies arrive, and beg that the Editor will instantly abandon all his duties [..]