from django.contrib.contenttypes.models import ContentType
from comments.models import Comment
def post_detail(request, slug=None):
    content_type = ContentType.objects.get_for_model(Post)
    obj_id = instance.id
    comments = Comment.objects.filter(content_type=content_type,object_id=obj_id)   
    context = {
        "title" : instance.title,
        "instance" : instance,
        "share_string":share_string,
        "comments":comments,
    }
    return render(request, "post_detail.html",context)  

<p>Comments</p>
{% for comment in comments %}
{{comment.content_object}}
<div class="">
    {{comment.content}}
    <br/>
    via {{comment.user }} | {{comment.timestamp|timesince}} ago
</div>
{% endfor %}