it works!!

lib/pleroma/notification.ex

@@ -6,6 +6,7 @@ defmodule Pleroma.Notification do
   use Ecto.Schema
   alias Pleroma.{User, Activity, Notification, Repo}
   alias Pleroma.Web.CommonAPI.Utils
+  alias Pleroma.Web.ThreadMute
   import Ecto.Query
 
   schema "notifications" do
@@ -112,6 +113,7 @@ defmodule Pleroma.Notification do
   # TODO move to sql, too.
   def create_notification(%Activity{} = activity, %User{} = user) do
     unless User.blocks?(user, %{ap_id: activity.data["actor"]}) or
+             ThreadMute.muted?(user, activity) or
              user.ap_id == activity.data["actor"] or
              (activity.data["type"] == "Follow" and
                 Enum.any?(Notification.for_user(user), fn notif ->

lib/pleroma/web/thread_mute.ex

@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Web.ThreadMute do
   use Ecto.Schema
+  alias Pleroma.Web.ThreadMute
   alias Pleroma.{Activity, Repo, User}
   require Ecto.Query
 
@@ -13,16 +14,37 @@ defmodule Pleroma.Web.ThreadMute do
   end
 
   def add_mute(user, id) do
-    %{data: %{"context" => context}} = Activity.get_by_id(id)
+    activity = Activity.get_by_id(id)
+    context = activity.data["context"]
     mute = %Pleroma.Web.ThreadMute{user_id: user.id, context: context}
     Repo.insert(mute)
+    {:ok, activity}
   end
 
   def remove_mute(user, id) do
     user_id = Pleroma.FlakeId.from_string(user.id)
-    %{data: %{"context" => context}} = Activity.get_by_id(id)
+    activity = Activity.get_by_id(id)
+    context = activity.data["context"]
 
-    Ecto.Query.from(m in "thread_mutes", where: m.user_id == ^user_id and m.context == ^context)
+    Ecto.Query.from(m in ThreadMute, where: m.user_id == ^user_id and m.context == ^context)
     |> Repo.delete_all()
+
+    {:ok, activity}
+  end
+
+  def muted?(user, activity) do
+    user_id = Pleroma.FlakeId.from_string(user.id)
+    context = activity.data["context"]
+
+    result =
+      Ecto.Query.from(m in ThreadMute,
+        where: m.user_id == ^user_id and m.context == ^context
+      )
+      |> Repo.all()
+
+    case result do
+      [] -> false
+      _ -> true
+    end
   end
 end