diff --git a/pages.py b/pages.py
index dbb8557..c3d5694 100644
--- a/pages.py
+++ b/pages.py
@@ -43,11 +43,11 @@ def load_user(protocol, id):
     Raises:
       :class:`werkzeug.exceptions.HTTPException` on error or redirect
     """
+    assert id
     cls = PROTOCOLS[protocol]
     g.user = cls.get_by_id(id)
 
-    # TODO(#512): generalize across protocols
-    if protocol == 'activitypub':
+    if protocol != 'web':
         if not g.user:
             g.user = cls.query(cls.readable_id == id).get()
             if g.user and g.user.use_instead:
diff --git a/protocol.py b/protocol.py
index 85656e2..09e3498 100644
--- a/protocol.py
+++ b/protocol.py
@@ -45,6 +45,7 @@ objects_cache_lock = threading.Lock()
 logger = logging.getLogger(__name__)
 
 
+# TODO: merge Protocol and User classes?
 class Protocol:
     """Base protocol class. Not to be instantiated; classmethods only.
 
@@ -173,8 +174,8 @@ class Protocol:
                 error(f'Undo of Follow requires actor id and object id. Got: {actor_id} {inner_obj_id} {obj.as1}')
 
             # deactivate Follower
-            # TODO(#512): generalize across protocols
-            # TODO(#512): merge Protocol and User
+            # TODO(#512): generalize across protocols. use inner_obj_id's
+            # brid.gy subdomain to determine protocol?
             followee_domain = util.domain_from_link(inner_obj_id, minimize=False)
             from web import Web
             follower = Follower.query(
@@ -372,17 +373,16 @@ class Protocol:
 
             # TODO(#512): generalize protocol
             from web import Web
-            recip = Web(id=domain).key
-            if recip not in obj.users:
-                if not recip.get():
+            recip = Web(id=domain)
+            if recip.key not in obj.users:
+                if not recip.key.get():
                     logger.info(f'No Web user for {domain}; skipping {target.uri}')
                     no_user_domains.add(domain)
                     continue
-                obj.users.append(recip)
+                obj.users.append(recip.key)
 
             try:
-                # TODO(#512): generalize protocol
-                if Web.send(obj, target.uri):
+                if recip.send(obj, target.uri):
                     obj.delivered.append(target)
                     if 'notification' not in obj.labels:
                         obj.labels.append('notification')
diff --git a/redirect.py b/redirect.py
index f46a4da..e3ec87c 100644
--- a/redirect.py
+++ b/redirect.py
@@ -1,14 +1,18 @@
 """Simple conneg endpoint that serves AS2 or redirects to to the original post.
 
-Serves /r/https://foo.com/bar URL paths, where https://foo.com/bar is an
-original post. Needed for Mastodon interop, they require that AS2 object ids and
-urls are on the same domain that serves them. Background:
+Only for Web users. Other protocols (including Web sometimes) use /convert/ in
+convert.py instead.
+
+Serves /r/https://foo.com/bar URL paths, where https://foo.com/bar is a original
+post for a Web user. Needed for Mastodon interop, they require that AS2 object
+ids and urls are on the same domain that serves them. Background:
 
 https://github.com/snarfed/bridgy-fed/issues/16#issuecomment-424799599
 https://github.com/tootsuite/mastodon/pull/6219#issuecomment-429142747
 
 The conneg makes these /r/ URLs searchable in Mastodon:
 https://github.com/snarfed/bridgy-fed/issues/352
+
 """
 import logging
 import re
@@ -76,8 +80,6 @@ def redir(to):
                    to_domain))
     for domain in domains:
         if domain:
-            # TODO(#512): do we need to parameterize this by protocol? or is it
-            # only for web?
             g.user = Web.get_by_id(domain)
             if g.user:
                 logger.info(f'Found web user for domain {domain}')
diff --git a/tests/testutil.py b/tests/testutil.py
index 152d234..4a26ce6 100644
--- a/tests/testutil.py
+++ b/tests/testutil.py
@@ -163,7 +163,7 @@ class TestCase(unittest.TestCase, testutil.Asserts):
         result.failures = prune(result.failures)
         return result
 
-    # TODO(#512): switch default to Fake, start using that more
+    # TODO: switch default to Fake, start using that more
     @staticmethod
     def make_user(id, cls=Web, **kwargs):
         """Reuse RSA key across Users because generating it is expensive."""