It may be that the problem is due to the way the current scim architecture interacts with gedit-- rather than the m17n package. This indeed seems likely, for the following reasons:
1) m17n package works fine in gedit when used through ibus or Fcitx. So it is specifically scim that is unable to utilize m17n properly in gedit.
2) The very same problem with scim and defective functionality of backspace and delete keys, is found when typing in Nemo file browser. For example if one is renaming a file in Nemo using scim, then the backspace and delete keys are dysfunctional.
It may be that the problem is due to the way the current scim architecture interacts with gedit-- rather than the m17n package. This indeed seems likely, for the following reasons:
1) m17n package works fine in gedit when used through ibus or Fcitx. So it is specifically scim that is unable to utilize m17n properly in gedit.
2) The very same problem with scim and defective functionality of backspace and delete keys, is found when typing in Nemo file browser. For example if one is renaming a file in Nemo using scim, then the backspace and delete keys are dysfunctional.