The AngularJS compiler processes (parts of) the DOM, determining which directives match which DOM elements, and then applies the directives to the elements. Each DOM element should only be compiled once, otherwise unexpected behavior may result.

Only compile new DOM elements.

The following example (adapted from the AngularJS developer guide) shows a directive that adds a tooltip to a DOM element, and then compiles the entire element to apply nested directives.

This is problematic, since it will recompile all of element, including parts that have already been compiled.

Instead, only the new element should be compiled:

AngularJS Developer Guide: Double Compilation, and how to avoid it.