Modify marshmallow calls & as per Deimos suggestions in !21

tildes/tildes/views/api/web/comment.py

@@ -1,7 +1,6 @@
 """Web API endpoints related to comments."""
 
-from marshmallow.fields import String
-from marshmallow.validate import OneOf
+from marshmallow.fields import Boolean
 from pyramid.request import Request
 from pyramid.response import Response
 from sqlalchemy.dialects.postgresql import insert
@@ -59,8 +58,6 @@ def _increment_topic_comments_seen(
         request.db_session.execute(statement)
         mark_changed(request.db_session)
 
-    return
-
 
 @ic_view_config(
     route_name='topic_comments',
@@ -327,26 +324,21 @@ def untag_comment(request: Request, name: CommentTagOption) -> Response:
     request_method='PUT',
     permission='mark_read',
 )
-@use_kwargs({
-    'clear_all_previous': String(
-        load_from='mark_all_previous',
-        validate=OneOf(('true', 'false')),
-    ),
-})
+@use_kwargs({'mark_all_previous': Boolean(missing=False,)})
 def put_mark_comments_read(
         request: Request,
-        clear_all_previous: str = 'false'
+        mark_all_previous: bool,
 ) -> Response:
     """Mark comment(s) read clearing notifications.
 
     comment(s) are removed from unread_notifications and the from topics
-    'new' count. If the query param clear_all_previous is 'true' all
+    'new' count. If the query param mark_all_previous is Truthy all
     notifications prior to the target will be cleared.
     """
     comment = request.context
     response = IC_NOOP
 
-    if clear_all_previous == 'true':
+    if mark_all_previous is True:
         prev_notifications = (
             request.query(CommentNotification).filter(
                 CommentNotification.is_unread == True, #noqa