This is required in order for mprdb to play nicely with dumb spectation systems, such as termcast and dgamelaunch. 200 is an empirical number chosen such as to not quite fill up termcast's 100KB output buffer; dgamelaunch has an unlimited output buffer, but takes linear space, so anything much larger than 200 would be unwise.
The opens the pathway to someday support message history. More importantly, ncurses interprets the use of addch() scrolling as a license to ignore idlok. Changing this fixes the "termcast screen shredding" issue.
This means that if the game crashes, you don't lose your save. This also means that it's possible to cheat with signals and power cuts. I don't see this as a big problem, since you can already cheat with cp (and ptrace, which uses the same access checks as non-terminal signals).