The app had favoured original content in its "stories" feature over existing, re-shared posts, but will now give them equal treatment, it said.
The current system had a "bigger impact than expected" on some types of posts.
But that was an unintended side-effect rather than an attempt to censor any particular viewpoint, Instagram said.
During the recent Gaza conflict, social media platforms were heavily used to spread messages of support on both sides.
Many pro-Palestinian messages were among those widely re-shared - which means they would have received less prominence than original posts under the current system.