Use the Atom package manager, which can be found in the Settings view or run
apm install dotject from the command line.
Highlight your dotject string and use
shift-cmd-J (default) to perform the conversion.
a.b.c,d.e then pressing
shift-cmd-J will replace the dotject with:
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.