Add a description in a code for the fix. Improve name of the unit test.

src/model/utils/insertcontent.js

@@ -561,7 +561,14 @@ class Insertion {
 				this.position = this.writer.createPositionBefore( parent );
 
 				// Special case – parent is empty (<p>^</p>).
+				//
+				// 1. parent.isEmpty
 				// We can remove the element after moving insertion position out of it.
+				//
+				// 2. parent.parent === allowedIn
+				// However parent should remain in place when allowed element is above limit element in document tree.
+				// For example there shouldn't be allowed to remove empty paragraph from tableCell, when is pasted
+				// content allowed in $root.
 				if ( parent.isEmpty && parent.parent === allowedIn ) {
 					this.writer.remove( parent );
 				}

tests/model/utils/insertcontent.js

@@ -1255,7 +1255,7 @@ describe( 'DataController utils', () => {
 			expect( stringify( root, affectedRange ) ).to.equal( '<limit>[ab]foo</limit>' );
 		} );
 
-		describe( 'when allowed elements is somewhere above limit', () => {
+		describe( 'when allowed element is above limit element in document tree', () => {
 			// $root > table > tableRow > tableCell > paragraph
 			// After inserting new table ( allowed in root ), empty paragraph shouldn't be removed from current tableCell.
 			beforeEach( () => {