Canvas - My students can't see other sections students of a cross-listed course.
Starting Fall 2017 users are only allowed to see users enrolled in the same section. The exception being the instructors of lecture sections.
Limiting students to "interact by section" only affects Collaborations, Chat, People, and Conversations. When enrolling instructors and TAs, section limitations allow those users to grade students in their same section(s).
Discussion topics and Pages are not affected by section limitations and can be viewed by any student. These feature areas could be restricted by creating content in course groups.
If there is a pedagogic need for interaction across sections, it is recommended instructors add a section to their course and enroll the users who require interaction.
Relevant Canvas Guides:
How do I add a section to a course?
How do I edit sections for an enrollment?