diff --git a/src/main/scala/app/IssuesController.scala b/src/main/scala/app/IssuesController.scala
index f62b86f..22544e7 100644
--- a/src/main/scala/app/IssuesController.scala
+++ b/src/main/scala/app/IssuesController.scala
@@ -14,7 +14,7 @@
   with ReadableUsersAuthenticator with ReferrerAuthenticator with CollaboratorsAuthenticator
 
 trait IssuesControllerBase extends ControllerBase {
-  self: IssuesService with RepositoryService with LabelsService with MilestonesService with ActivityService
+  self: IssuesService with RepositoryService with AccountService with LabelsService with MilestonesService with ActivityService
     with ReadableUsersAuthenticator with ReferrerAuthenticator with CollaboratorsAuthenticator =>
 
   case class IssueCreateForm(title: String, content: Option[String],
@@ -65,7 +65,7 @@
           _,
           getComments(owner, name, issueId.toInt),
           getIssueLabels(owner, name, issueId.toInt),
-          (getCollaborators(owner, name) :+ owner).sorted,
+          (getCollaborators(owner, name) ::: (if(getAccountByUserName(owner).get.isGroupAccount) Nil else List(owner))).sorted,
           getMilestonesWithIssueCount(owner, name),
           getLabels(owner, name),
           hasWritePermission(owner, name, context.loginAccount),
@@ -77,7 +77,7 @@
   get("/:owner/:repository/issues/new")(readableUsersOnly { repository =>
     defining(repository.owner, repository.name){ case (owner, name) =>
       issues.html.create(
-          (getCollaborators(owner, name) :+ owner).sorted,
+        (getCollaborators(owner, name) ::: (if(getAccountByUserName(owner).get.isGroupAccount) Nil else List(owner))).sorted,
           getMilestones(owner, name),
           getLabels(owner, name),
           hasWritePermission(owner, name, context.loginAccount),
diff --git a/src/main/scala/app/PullRequestsController.scala b/src/main/scala/app/PullRequestsController.scala
index c234bc6..9e811ef 100644
--- a/src/main/scala/app/PullRequestsController.scala
+++ b/src/main/scala/app/PullRequestsController.scala
@@ -24,7 +24,7 @@
   with ReferrerAuthenticator with CollaboratorsAuthenticator
 
 trait PullRequestsControllerBase extends ControllerBase {
-  self: RepositoryService with IssuesService with MilestonesService with ActivityService with PullRequestService
+  self: RepositoryService with AccountService with IssuesService with MilestonesService with ActivityService with PullRequestService
     with ReferrerAuthenticator with CollaboratorsAuthenticator =>
 
   val pullRequestForm = mapping(
@@ -74,7 +74,7 @@
           pulls.html.pullreq(
             issue, pullreq,
             getComments(owner, name, issueId),
-            (getCollaborators(owner, name) :+ owner).sorted,
+            (getCollaborators(owner, name) ::: (if(getAccountByUserName(owner).get.isGroupAccount) Nil else List(owner))).sorted,
             getMilestonesWithIssueCount(owner, name),
             commits,
             diffs,
diff --git a/src/main/scala/app/RepositorySettingsController.scala b/src/main/scala/app/RepositorySettingsController.scala
index a9285fd..cd2b47f 100644
--- a/src/main/scala/app/RepositorySettingsController.scala
+++ b/src/main/scala/app/RepositorySettingsController.scala
@@ -188,6 +188,8 @@
     override def validate(name: String, value: String): Option[String] =
       getAccountByUserName(value) match {
         case None => Some("User does not exist.")
+        case Some(x) if(x.isGroupAccount)
+                  => Some("User does not exist.")
         case Some(x) if(x.userName == params("owner") || getCollaborators(params("owner"), params("repository")).contains(x.userName))
                   => Some("User can access this repository already.")
         case _    => None
diff --git a/src/main/scala/servlet/GitRepositoryServlet.scala b/src/main/scala/servlet/GitRepositoryServlet.scala
index e16f48c..1ae0062 100644
--- a/src/main/scala/servlet/GitRepositoryServlet.scala
+++ b/src/main/scala/servlet/GitRepositoryServlet.scala
@@ -149,7 +149,7 @@
     "(^|\\W)#(\\d+)(\\W|$)".r.findAllIn(commit.fullMessage).matchData.foreach { matchData =>
       val issueId = matchData.group(2)
       if(getAccountByUserName(commit.committer).isDefined && getIssue(owner, repository, issueId).isDefined){
-        createComment(owner, repository, commit.committer, issueId.toInt, commit.fullMessage, "commit")
+        createComment(owner, repository, commit.committer, issueId.toInt, commit.id + " " + commit.fullMessage, "commit")
       }
     }
   }
diff --git a/src/main/twirl/issues/commentlist.scala.html b/src/main/twirl/issues/commentlist.scala.html
index 3c19aa4..4071dcf 100644
--- a/src/main/twirl/issues/commentlist.scala.html
+++ b/src/main/twirl/issues/commentlist.scala.html
@@ -21,7 +21,14 @@
         </span>
       </div>
       <div class="box-content"class="issue-content" id="commentContent-@comment.commentId">
-        @markdown(comment.content, repository, false, true)
+        @if(comment.action == "commit" && comment.content.split(" ").last.matches("[a-f0-9]{40}")){
+          @defining(comment.content.substring(comment.content.length - 40)){ id =>
+            <div class="pull-right"><a href="@path/@repository.owner/@repository.name/commit/@id" class="monospace">@id.substring(0, 7)</a></div>
+            @markdown(comment.content.substring(0, comment.content.length - 41), repository, false, true)
+          }
+        } else {
+          @markdown(comment.content, repository, false, true)
+        }
       </div>
     </div>
   }