diff --git a/app/models/topic.rb b/app/models/topic.rb
index 961d8f2..588971f 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -49,6 +49,61 @@ def participant_aliases(limit: 10)
     participants
   end
 
+  def participant_alias_stats(limit: 10)
+    stats = messages.group(:sender_id)
+                    .select('sender_id, COUNT(*) as message_count, MAX(messages.created_at) AS last_at')
+                    .order('message_count DESC')
+                    .limit(50)
+                    .index_by(&:sender_id)
+
+    first_sender = messages.order(:created_at).first&.sender
+    last_sender = messages.order(:created_at).last&.sender
+
+    missing_ids = [first_sender&.id, last_sender&.id].compact.uniq - stats.keys
+    if missing_ids.any?
+      extra_stats = messages.where(sender_id: missing_ids)
+                            .group(:sender_id)
+                            .select('sender_id, COUNT(*) as message_count, MAX(messages.created_at) AS last_at')
+                            .index_by(&:sender_id)
+      stats.merge!(extra_stats)
+    end
+
+    sender_ids = stats.keys
+    senders_by_id = Alias.includes(person: :contributor_memberships).where(id: sender_ids).index_by(&:id)
+
+    entry_for = lambda do |alias_record|
+      return nil unless alias_record
+
+      stat = stats[alias_record.id]
+      {
+        alias: alias_record,
+        message_count: stat&.read_attribute(:message_count)&.to_i,
+        last_at: stat&.read_attribute(:last_at)
+      }
+    end
+
+    participants = []
+
+    participants << entry_for.call(first_sender) if first_sender
+
+    first_and_last = [first_sender&.id, last_sender&.id].compact.uniq
+    other_senders = sender_ids - first_and_last
+    remaining = [limit - first_and_last.length, 0].max
+    other_participants = other_senders
+      .map { |id| senders_by_id[id] }
+      .compact
+      .sort_by { |s| -stats[s.id].read_attribute(:message_count).to_i }
+      .take(remaining)
+
+    participants.concat(other_participants.map { |alias_record| entry_for.call(alias_record) }.compact)
+
+    if last_sender && last_sender.id != first_sender&.id
+      participants << entry_for.call(last_sender)
+    end
+
+    participants.compact
+  end
+
   def has_contributor_activity?
     @has_contributor_activity ||= begin
       contributor_people = ContributorMembership.select(:person_id).distinct
diff --git a/app/views/topics/_avatar_list.slim b/app/views/topics/_avatar_list.slim
index bd814ee..0fc3cba 100644
--- a/app/views/topics/_avatar_list.slim
+++ b/app/views/topics/_avatar_list.slim
@@ -1,15 +1,23 @@
 .participants
   .participants-avatars
     - participants.each do |participant|
+      - alias_record = participant[:alias] || participant
+      - next unless alias_record
+      - message_count = participant[:message_count]
+      - last_at = participant[:last_at]
+      - tooltip_parts = []
+      - tooltip_parts << pluralize(message_count, "message") if message_count
+      - tooltip_parts << "last #{smart_time_display(last_at)}" if last_at
+      - role_label = alias_record.contributor_badge || "User"
+      - tooltip_parts << role_label
+      - badge_text = tooltip_parts.any? ? tooltip_parts.join(", ") : "#{alias_record.name} (#{role_label})"
       - css_classes = ["participant-avatar"]
-      - css_classes << "is-core-team" if participant.core_team?
-      - css_classes << "is-committer" if !participant.core_team? && participant.committer?
-      - css_classes << "is-major-contributor" if !participant.core_team? && !participant.committer? && participant.major_contributor?
-      - css_classes << "is-significant-contributor" if !participant.core_team? && !participant.committer? && !participant.major_contributor? && participant.significant_contributor?
-      - css_classes << "is-past-contributor" if participant.past_contributor?
-      - role_label = participant.contributor_badge || "User"
-      - badge_text = "#{participant.name} (#{role_label})"
-      = link_to person_path(participant.email), class: "participant-avatar-link" do
-        = image_tag participant.display_gravatar_url(size: 32), class: css_classes.join(" "), alt: participant.name, title: badge_text
+      - css_classes << "is-core-team" if alias_record.core_team?
+      - css_classes << "is-committer" if !alias_record.core_team? && alias_record.committer?
+      - css_classes << "is-major-contributor" if !alias_record.core_team? && !alias_record.committer? && alias_record.major_contributor?
+      - css_classes << "is-significant-contributor" if !alias_record.core_team? && !alias_record.committer? && !alias_record.major_contributor? && alias_record.significant_contributor?
+      - css_classes << "is-past-contributor" if alias_record.past_contributor?
+      = link_to person_path(alias_record.email), class: "participant-avatar-link" do
+        = image_tag alias_record.display_gravatar_url(size: 32), class: css_classes.join(" "), alt: alias_record.name, title: badge_text
     - if total_participants > participants.count
       span.participants-count +#{total_participants - participants.count}
diff --git a/app/views/topics/_topic_row_user.html.slim b/app/views/topics/_topic_row_user.html.slim
index 229f1fc..037379c 100644
--- a/app/views/topics/_topic_row_user.html.slim
+++ b/app/views/topics/_topic_row_user.html.slim
@@ -13,7 +13,7 @@ tr id=dom_id(topic) class="topic-row topic-#{state[:status] || 'new'}" data-topi
       .activity-replies = pluralize(replies_count, "reply")
       .activity-time title=absolute_time_display(last_message.created_at) = smart_time_display(last_message.created_at)
   td.topic-participants data-label="Participants"
-    - participants = topic.participant_aliases(limit: 5)
+    - participants = topic.participant_alias_stats(limit: 5)
     - participant_count = topic.participant_count
     = render partial: "avatar_list", locals: { participants: participants, total_participants: participant_count }
     - if topic.has_contributor_activity?
diff --git a/app/views/topics/_topics.html.slim b/app/views/topics/_topics.html.slim
index bff2014..c729074 100644
--- a/app/views/topics/_topics.html.slim
+++ b/app/views/topics/_topics.html.slim
@@ -8,7 +8,7 @@
         .activity-replies = pluralize(replies_count, "reply")
         .activity-time title=absolute_time_display(last_message.created_at) = smart_time_display(last_message.created_at)
     td.topic-participants data-label="Participants"
-      - participants = topic.participant_aliases(limit: 5)
+      - participants = topic.participant_alias_stats(limit: 5)
       - participant_count = topic.participant_count
       = render partial: "avatar_list", locals: { participants: participants, total_participants: participant_count }
       - if topic.has_contributor_activity?