class Muro(models.Model):

    tema = models.ForeignKey(Tematica,
        on_delete=models.CASCADE,
        verbose_name="Tematica",
    )
    ...

class Historias(models.Model):

    muro = models.ForeignKey(Muro,
        on_delete=models.CASCADE,
        verbose_name="Muro",
    )
    ...


class Comentarios(models.Model):

    historia = models.ForeignKey(Historias,
        on_delete=models.CASCADE,
        verbose_name="Historia",
    )
    ...

def muro(request, pk):

    cabeceraMuro = Muro.objects.get(pk=pk)
    historias = Historias.objects.filter(muro__pk=pk)
    comentarios = Comentarios.objects.filter(historia__muro__pk=pk)

    context = {
        'cabeceraMuro': cabeceraMuro,
        'historias': historias,
        'comentarios': comentarios,
    }
    return render(request, 'muro.html', context)

{% for historia in historias %}

<h1>Historia</h1>
...
<p>{{ historia.nombre }}</p>
<p>...</p>
...

<h3>Comentarios de la historia</h3>

{% for coment in comentarios %}
...
<p>{{ coment.comentario }}</p>
<p>...</p>
...

{% endfor %}

{% endfor %}

class Muro(models.Model):

    tema = models.ForeignKey(Tematica,
        on_delete=models.CASCADE,
        verbose_name="Tematica",
    )
    ...

class Historias(models.Model):

    muro = models.ForeignKey(Muro,
        on_delete=models.CASCADE,
        verbose_name="Muro",
    )
    ...


class Comentarios(models.Model):

    historia = models.ForeignKey(Historias,
        on_delete=models.CASCADE,
        verbose_name="Historia",
        related_name="comentariosHistoria",
    )
    ...

def muro(request, pk):

    cabeceraMuro = Muro.objects.get(pk=pk)
    historias = Historias.objects.filter(muro__pk=pk)

    context = {
        'cabeceraMuro': cabeceraMuro,
        'historias': historias,
    }
    return render(request, 'muro.html', context)

{% for historia in historias %}

<h1>Historia</h1>
...
<p>{{ historia.nombre }}</p>
<p>...</p>
...

<h3>Comentarios de la historia</h3>

{% for coment in historia.comentariosHistoria.all %}
...
<p>{{ coment.comentario }}</p>
<p>...</p>
...

{% endfor %}

{% endfor %}