39 files declare their use of CommentInterface in Drupal 8

BigPipeRegressionTest.php in core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php

comment.api.php in core/modules/comment/comment.api.php

Hooks provided by the Comment module.

comment.module in core/modules/comment/comment.module

Enables users to comment on published content.

Comment.php in core/modules/comment/src/Entity/Comment.php

CommentAdminOverview.php in core/modules/comment/src/Form/CommentAdminOverview.php

CommentAnonymousTest.php in core/modules/comment/tests/src/Functional/CommentAnonymousTest.php

CommentAttributesTest.php in core/modules/rdf/tests/src/Functional/CommentAttributesTest.php

CommentBaseFieldTest.php in core/modules/comment/tests/src/Kernel/CommentBaseFieldTest.php

CommentBookTest.php in core/modules/comment/tests/src/Functional/CommentBookTest.php

CommentCacheTagsTest.php in core/modules/comment/tests/src/Functional/CommentCacheTagsTest.php

CommentController.php in core/modules/comment/src/Controller/CommentController.php

CommentCSSTest.php in core/modules/comment/tests/src/Functional/CommentCSSTest.php

CommentDefaultFormatterCacheTagsTest.php in core/modules/comment/tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php

CommentEntityTest.php in core/modules/comment/tests/src/Functional/CommentEntityTest.php

CommentFieldAccessTest.php in core/modules/comment/tests/src/Kernel/CommentFieldAccessTest.php

CommentItem.php in core/modules/comment/src/Plugin/Field/FieldType/CommentItem.php

CommentLegacyTest.php in core/modules/comment/tests/src/Kernel/CommentLegacyTest.php

CommentLinksTest.php in core/modules/comment/tests/src/Functional/CommentLinksTest.php

CommentNameConstraintValidator.php in core/modules/comment/src/Plugin/Validation/Constraint/CommentNameConstraintValidator.php

CommentNewIndicatorTest.php in core/modules/comment/tests/src/Functional/CommentNewIndicatorTest.php

CommentNonNodeTest.php in core/modules/comment/tests/src/Functional/CommentNonNodeTest.php

CommentSelection.php in core/modules/comment/src/Plugin/EntityReferenceSelection/CommentSelection.php

CommentTestBase.php in core/modules/comment/src/Tests/CommentTestBase.php

CommentTestBase.php in core/modules/comment/tests/src/Functional/CommentTestBase.php

CommentTestController.php in core/modules/comment/tests/modules/comment_test/src/Controller/CommentTestController.php

CommentValidationTest.php in core/modules/comment/tests/src/Kernel/CommentValidationTest.php

comment_test.module in core/modules/comment/tests/modules/comment_test/comment_test.module

Dummy module implementing comment related hooks to test API interaction with the Comment module.

DefaultViewRecentCommentsTest.php in core/modules/comment/tests/src/Functional/Views/DefaultViewRecentCommentsTest.php

DefaultViewsTest.php in core/modules/views/tests/src/Functional/DefaultViewsTest.php

EntityFilteringThemeTest.php in core/modules/system/tests/src/Functional/Theme/EntityFilteringThemeTest.php

EntityReferenceSelectionAccessTest.php in core/modules/system/tests/src/Functional/Entity/EntityReferenceSelection/EntityReferenceSelectionAccessTest.php

forum.module in core/modules/forum/forum.module

Provides discussion forums.

ForumIndexStorage.php in core/modules/forum/src/ForumIndexStorage.php

ForumUninstallTest.php in core/modules/forum/tests/src/Functional/ForumUninstallTest.php

NodeAccessPagerTest.php in core/modules/node/tests/src/Functional/NodeAccessPagerTest.php

NodeNewComments.php in core/modules/comment/src/Plugin/views/field/NodeNewComments.php

tracker.module in core/modules/tracker/tracker.module

Tracks recent content posted by a user or users.

TrackerTest.php in core/modules/tracker/tests/src/Functional/TrackerTest.php

UserCancelTest.php in core/modules/user/tests/src/Functional/UserCancelTest.php