*nix configuration files always concatenatable

Linux and Unix configuration files that may need to be changed by the addition of extra programs, that is, files containing menus, mimetypes, startup script configurations etc. must not have any strong inherent structure, e.g. a header section of the file. Ideally, they would instead be perfectly concatenatable in any order, or at least, allow new programs to add lines at the bottom (by the >> operator) whose order does not affect operation. I suspect that menu configuration has already been more cleverly solved by the large desktop environments than to require programs to add their own menu items in the right places, but I'm just testing Arch Linux, and the configuration here is somewhat retrograde in that most of it is in one file, rc.conf, which is therefore highly structured.