diff --git a/web/components/contract-feed.tsx b/web/components/contract-feed.tsx
index 882ed416..49671d4c 100644
--- a/web/components/contract-feed.tsx
+++ b/web/components/contract-feed.tsx
@@ -13,7 +13,8 @@ import {
   XIcon,
 } from '@heroicons/react/solid'
 import { useBets } from '../hooks/use-bets'
-import { Bet, createComment } from '../lib/firebase/bets'
+import { Bet } from '../lib/firebase/bets'
+import { Comment, mapCommentsByBetId } from '../lib/firebase/comments'
 import dayjs from 'dayjs'
 import relativeTime from 'dayjs/plugin/relativeTime'
 import { OutcomeLabel } from './outcome-label'
@@ -21,6 +22,8 @@ import { Contract, setContract } from '../lib/firebase/contracts'
 import { useUser } from '../hooks/use-user'
 import { Linkify } from './linkify'
 import { Row } from './layout/row'
+import { createComment } from '../lib/firebase/comments'
+import { useComments } from '../hooks/use-comments'
 dayjs.extend(relativeTime)
 
 function FeedComment(props: { activityItem: any }) {
@@ -289,7 +292,7 @@ function toFeedBet(bet: Bet) {
   }
 }
 
-function toComment(bet: Bet) {
+function toFeedComment(bet: Bet, comment: Comment) {
   return {
     id: bet.id,
     contractId: bet.contractId,
@@ -301,25 +304,22 @@ function toComment(bet: Bet) {
     date: dayjs(bet.createdTime).fromNow(),
 
     // Invariant: bet.comment exists
-    text: bet.comment!.text,
+    text: comment.text,
     person: {
-      href: `/${bet.comment!.userUsername}`,
-      name: bet.comment!.userName,
-      avatarUrl: bet.comment!.userAvatarUrl,
+      href: `/${comment.userUsername}`,
+      name: comment.userName,
+      avatarUrl: comment.userAvatarUrl,
     },
   }
 }
 
-function toActivityItem(bet: Bet) {
-  return bet.comment ? toComment(bet) : toFeedBet(bet)
-}
-
 // Group together bets that are:
 // - Within 24h of the first in the group
 // - Do not have a comment
 // - Were not created by this user
 // Return a list of ActivityItems
-function group(bets: Bet[], userId?: string) {
+function group(bets: Bet[], comments: Comment[], userId?: string) {
+  const commentsMap = mapCommentsByBetId(comments)
   const items: any[] = []
   let group: Bet[] = []
 
@@ -328,15 +328,20 @@ function group(bets: Bet[], userId?: string) {
     if (group.length == 1) {
       items.push(toActivityItem(group[0]))
     } else if (group.length > 1) {
-      items.push({ type: 'betgroup', bets: [...group] })
+      items.push({ type: 'betgroup', bets: [...group], id: group[0].id })
     }
     group = []
   }
 
+  function toActivityItem(bet: Bet) {
+    const comment = commentsMap[bet.id]
+    return comment ? toFeedComment(bet, comment) : toFeedBet(bet)
+  }
+
   for (const bet of bets) {
     const isCreator = userId === bet.userId
 
-    if (bet.comment || isCreator) {
+    if (commentsMap[bet.id] || isCreator) {
       pushGroup()
       // Create a single item for this
       items.push(toActivityItem(bet))
@@ -417,7 +422,13 @@ export function ContractFeed(props: { contract: Contract }) {
   let bets = useBets(id)
   if (bets === 'loading') bets = []
 
-  const allItems = [{ type: 'start', id: 0 }, ...group(bets, user?.id)]
+  let comments = useComments(id)
+  if (comments === 'loading') comments = []
+
+  const allItems = [
+    { type: 'start', id: 0 },
+    ...group(bets, comments, user?.id),
+  ]
   if (contract.closeTime) {
     allItems.push({ type: 'close', id: `${contract.closeTime}` })
   }
diff --git a/web/hooks/use-comments.ts b/web/hooks/use-comments.ts
new file mode 100644
index 00000000..0a9dead3
--- /dev/null
+++ b/web/hooks/use-comments.ts
@@ -0,0 +1,12 @@
+import { useEffect, useState } from 'react'
+import { Comment, listenForComments } from '../lib/firebase/comments'
+
+export const useComments = (contractId: string) => {
+  const [comments, setComments] = useState<Comment[] | 'loading'>('loading')
+
+  useEffect(() => {
+    if (contractId) return listenForComments(contractId, setComments)
+  }, [contractId])
+
+  return comments
+}
diff --git a/web/lib/firebase/bets.ts b/web/lib/firebase/bets.ts
index 5df0b543..49d92e0e 100644
--- a/web/lib/firebase/bets.ts
+++ b/web/lib/firebase/bets.ts
@@ -4,11 +4,8 @@ import {
   query,
   onSnapshot,
   where,
-  doc,
-  updateDoc,
 } from 'firebase/firestore'
 import { db } from './init'
-import { User } from './users'
 
 export type Bet = {
   id: string
@@ -31,16 +28,6 @@ export type Bet = {
   isSold?: boolean // true if this BUY bet has been sold
 
   createdTime: number
-
-  // Currently, comments are created after the bet, not atomically with the bet.
-  comment?: {
-    text: string
-    createdTime: number
-    // Denormalized, for rendering comments
-    userName?: string
-    userUsername?: string
-    userAvatarUrl?: string
-  }
 }
 
 function getBetsCollection(contractId: string) {
@@ -75,21 +62,3 @@ export function listenForUserBets(
     setBets(bets)
   })
 }
-
-export async function createComment(
-  contractId: string,
-  betId: string,
-  text: string,
-  commenter: User
-) {
-  const betRef = doc(getBetsCollection(contractId), betId)
-  return await updateDoc(betRef, {
-    comment: {
-      text: text,
-      createdTime: Date.now(),
-      userName: commenter.name,
-      userUsername: commenter.username,
-      userAvatarUrl: commenter.avatarUrl,
-    },
-  })
-}
diff --git a/web/lib/firebase/comments.ts b/web/lib/firebase/comments.ts
new file mode 100644
index 00000000..d46c6ee9
--- /dev/null
+++ b/web/lib/firebase/comments.ts
@@ -0,0 +1,60 @@
+import { doc, collection, onSnapshot, setDoc } from 'firebase/firestore'
+import { db } from './init'
+import { User } from './users'
+
+// Currently, comments are created after the bet, not atomically with the bet.
+// They're uniquely identified by the pair contractId/betId.
+export type Comment = {
+  contractId: string
+  betId: string
+  text: string
+  createdTime: number
+  // Denormalized, for rendering comments
+  userName?: string
+  userUsername?: string
+  userAvatarUrl?: string
+}
+
+export async function createComment(
+  contractId: string,
+  betId: string,
+  text: string,
+  commenter: User
+) {
+  const ref = doc(getCommentsCollection(contractId), betId)
+  return await setDoc(ref, {
+    contractId,
+    betId,
+    text,
+    createdTime: Date.now(),
+    userName: commenter.name,
+    userUsername: commenter.username,
+    userAvatarUrl: commenter.avatarUrl,
+  })
+}
+
+function getCommentsCollection(contractId: string) {
+  return collection(db, 'contracts', contractId, 'comments')
+}
+
+export function listenForComments(
+  contractId: string,
+  setComments: (comments: Comment[]) => void
+) {
+  return onSnapshot(getCommentsCollection(contractId), (snap) => {
+    const comments = snap.docs.map((doc) => doc.data() as Comment)
+
+    comments.sort((c1, c2) => c1.createdTime - c2.createdTime)
+
+    setComments(comments)
+  })
+}
+
+// Return a map of betId -> comment
+export function mapCommentsByBetId(comments: Comment[]) {
+  const map: Record<string, Comment> = {}
+  for (const comment of comments) {
+    map[comment.betId] = comment
+  }
+  return map
+}