Form alter breaks when the comment field isn't in the "full" view mode.

If you enable the field in the 'Default' viewmode it works.

Attached patch solve the problem for me.

I did a check on the parameter before passing it to Drupal\ajax_comments\FieldSettingsHelper::isEnabled()

I would be very interested in a solution which lets you configure the commented entities display mode, which is hardcoded as 'full' (in in the function itself defaults to 'default') as already mentioned..

I cant seem to figure out a way to get the currently rendered view_mode of the parent entity at those 4 points in the code the current patch is editing to get rid of an error.

in Drupal 8.4.3 + ajax_comments 8.x-1.0-beta1
when the comment field isn't in the "full" view mode, i see error

TypeError: Argument 1 passed to Drupal\ajax_comments\FieldSettingsHelper::isEnabled() must implement interface Drupal\Core\Field\FormatterInterface, boolean given, called in /var/www/html/modules/contrib/ajax_comments/ajax_comments.module on line 44 in Drupal\ajax_comments\FieldSettingsHelper->isEnabled() (line 160 of /var/www/html/modules/contrib/ajax_comments/src/FieldSettingsHelper.php) #0 /var/www/html/modules/contrib/ajax_comments/ajax_comments.module(44): Drupal\ajax_comments\FieldSettingsHelper->isEnabled(false) 
#1 /var/www/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(501): ajax_comments_comment_links_alter(Array, Object(Drupal\comment\Entity\Comment), Array) 
#2 /var/www/html/core/modules/comment/src/CommentLazyBuilders.php(148): Drupal\Core\Extension\ModuleHandler->alter('comment_links', Array, Object(Drupal\comment\Entity\Comment), Array) 
#3 [internal function]: Drupal\comment\CommentLazyBuilders->renderLinks('5', 'token', 'uk', false) 
#4 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(358): call_user_func_array(Array, Array) 
#5 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(195): Drupal\Core\Render\Renderer->doRender(Array, true) 
#6 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(151): Drupal\Core\Render\Renderer->render(Array, true) 
#7 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(576): Drupal\Core\Render\Renderer->Drupal\Core\Render\{closure}() 
#8 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(152): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) 
#9 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(166): Drupal\Core\Render\Renderer->renderPlain(Array) 
#10 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(661): Drupal\Core\Render\Renderer->renderPlaceholder('<drupal-render-...', Array) 
#11 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(546): Drupal\Core\Render\Renderer->replacePlaceholders(Array) 
#12 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(195): Drupal\Core\Render\Renderer->doRender(Array, true) 
#13 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(139): Drupal\Core\Render\Renderer->render(Array, true) 
#14 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(576): Drupal\Core\Render\Renderer->Drupal\Core\Render\{closure}() 
#15 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(140): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) 
#16 /var/www/html/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php(258): Drupal\Core\Render\Renderer->renderRoot(Array) 
#17 /var/www/html/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php(131): Drupal\Core\Render\HtmlResponseAttachmentsProcessor->renderPlaceholders(Object(Drupal\Core\Render\HtmlResponse)) 
#18 /var/www/html/modules/contrib/http2_server_push/src/Render/HtmlResponseAttachmentsProcessor.php(48): Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAttachments(Object(Drupal\Core\Render\HtmlResponse)) 
#19 /var/www/html/core/lib/Drupal/Core/EventSubscriber/HtmlResponseSubscriber.php(45): Drupal\http2_server_push\Render\HtmlResponseAttachmentsProcessor->processAttachments(Object(Drupal\Core\Render\HtmlResponse)) 
#20 /var/www/html/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(108): Drupal\Core\EventSubscriber\HtmlResponseSubscriber->onRespond(Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent), 'kernel.response', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher)) 
#21 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(193): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.response', Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent)) 
#22 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(175): Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object(Drupal\Core\Render\HtmlResponse), Object(Symfony\Component\HttpFoundation\Request), 1) 
#23 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) 
#24 /var/www/html/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#25 /var/www/html/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#26 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#27 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#28 /var/www/html/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#29 /var/www/html/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#30 /var/www/html/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#31 /var/www/html/core/lib/Drupal/Core/DrupalKernel.php(657): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
#32 /var/www/html/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) 
#33 {main}.

patch #3 does not fix the bug

Same as number 5

Currently the implementation is attached to field configuration in node view modes, which introduces problems because it is in various comment contexts that we need to determine whether/how the behaviour should apply. An alternative that might address this issue (albeit with significant refactoring) is to make AJAX comments instead a property of comment view modes.

Updating the issue summary accordingly.

The hard-coding of view_mode definitely needs to go, and I don't see an easy way to do that without a new architecture because comments can be viewed on their own without the commented entity being called (and therefore no way to specific a view mode).

I agree with @nedjo.

An alternative that might address this issue (albeit with significant refactoring) is to make AJAX comments instead a property of comment view modes.

1+ !

At the moment, an attempt is being made to solve the problem in another issue #2896916: Ajax not working when using non-default view mode.