It seems that the ignore list accepts only file and folder names, not full path names. Is that correct? So suppose I have different files called main.c in several different folders (project1/main.c, project2/main.c, etc.) and there is one I don’t want to sync, but I do want to sync the others. Is that possible?
yes, this is being worked on for insync 3 with full path support.
This feature’s up on Insync beta 3.0.4 