diff --git a/ROADMAP.md b/ROADMAP.md
index 725a636..d801ac3 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -6,7 +6,6 @@ set, only a sequence of milestones and the requirements to hit them.
 
 ## Milestone: Be able to add other developers to the project
 
-* Thread commits (comments)
 * Coalesce command
 * Fast-forward perms on branches
 * Authorship in commit messages
diff --git a/cmd/dehub/cmd_commit.go b/cmd/dehub/cmd_commit.go
index 2810efd..eb2b19f 100644
--- a/cmd/dehub/cmd_commit.go
+++ b/cmd/dehub/cmd_commit.go
@@ -126,5 +126,29 @@ func cmdCommit(ctx context.Context, cmd *dcmd.Cmd) {
 		},
 	)
 
+	cmd.SubCmd("comment", "Commit a comment to a branch",
+		func(ctx context.Context, cmd *dcmd.Cmd) {
+			flag := cmd.FlagSet()
+			msg := flag.String("msg", "", "Comment message")
+			cmd.Run(func() (context.Context, error) {
+				if *msg == "" {
+					var err error
+					if *msg, err = tmpFileMsg(); err != nil {
+						return nil, fmt.Errorf("collecting comment message from user: %w", err)
+
+					} else if *msg == "" {
+						return nil, errors.New("empty comment message, not doing anything")
+					}
+				}
+
+				commit, err := repo.NewCommitComment(*msg)
+				if err != nil {
+					return nil, fmt.Errorf("constructing comment commit: %w", err)
+				}
+				return nil, accreditAndCommit(commit)
+			})
+		},
+	)
+
 	cmd.Run(body)
 }
diff --git a/cmd/dehub/tmp_file.go b/cmd/dehub/tmp_file.go
index 0354f8f..51437e5 100644
--- a/cmd/dehub/tmp_file.go
+++ b/cmd/dehub/tmp_file.go
@@ -29,7 +29,7 @@ func tmpFileMsg() (string, error) {
 
 	tmpBody := bytes.NewBufferString(`
 
-# Please enter the commit message for your changes. Lines starting
+# Please enter the commit message for your commit. Lines starting
 # with '#' will be ignored, and an empty message aborts the commit.`)
 
 	_, err = io.Copy(tmpf, tmpBody)
diff --git a/commit.go b/commit.go
index 8b6611f..7808d95 100644
--- a/commit.go
+++ b/commit.go
@@ -10,7 +10,9 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"reflect"
 	"sort"
+	"strings"
 	"time"
 
 	"gopkg.in/src-d/go-git.v4"
@@ -59,11 +61,23 @@ func (cc CommitCommon) credAccountIDs() []string {
 	return s
 }
 
+func abbrevCommitMessage(msg string) string {
+	i := strings.Index(msg, "\n")
+	if i > 0 {
+		msg = msg[:i]
+	}
+	if len(msg) > 80 {
+		msg = msg[:80] + "..."
+	}
+	return msg
+}
+
 // Commit represents a single Commit which is being added to a branch. Only one
 // field should be set on a Commit, unless otherwise noted.
 type Commit struct {
 	Change     *CommitChange     `type:"change,default"`
 	Credential *CommitCredential `type:"credential"`
+	Comment    *CommitComment    `type:"comment"`
 
 	Common CommitCommon `yaml:",inline"`
 }
@@ -133,7 +147,12 @@ func (c *Commit) UnmarshalText(msg []byte) error {
 
 	if err := yaml.Unmarshal(msgBody, c); err != nil {
 		return fmt.Errorf("could not unmarshal Commit message from yaml: %w", err)
+
+	} else if reflect.DeepEqual(*c, Commit{}) {
+		// a basic check, but worthwhile
+		return errors.New("commit message is malformed, could not unmarshal yaml object")
 	}
+
 	return nil
 }
 
diff --git a/commit_change.go b/commit_change.go
index 7608184..341639c 100644
--- a/commit_change.go
+++ b/commit_change.go
@@ -5,7 +5,6 @@ import (
 	"dehub/yamlutil"
 	"errors"
 	"fmt"
-	"strings"
 
 	"gopkg.in/src-d/go-git.v4/plumbing/object"
 )
@@ -46,11 +45,7 @@ func (r *Repo) NewCommitChange(msg string) (Commit, error) {
 
 // MessageHead implements the method for the CommitInterface interface.
 func (cc CommitChange) MessageHead(CommitCommon) (string, error) {
-	i := strings.Index(cc.Message, "\n")
-	if i > 0 {
-		return cc.Message[:i], nil
-	}
-	return cc.Message, nil
+	return abbrevCommitMessage(cc.Message), nil
 }
 
 // Hash implements the method for the CommitInterface interface.
diff --git a/commit_comment.go b/commit_comment.go
new file mode 100644
index 0000000..920855d
--- /dev/null
+++ b/commit_comment.go
@@ -0,0 +1,46 @@
+package dehub
+
+import (
+	"dehub/yamlutil"
+	"fmt"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
+)
+
+// CommitComment describes the structure of a comment commit message.
+type CommitComment struct {
+	Message     string        `yaml:"message"`
+	MessageHash yamlutil.Blob `yaml:"message_hash"`
+}
+
+var _ CommitInterface = CommitComment{}
+
+// NewCommitComment constructs and returns a COmmit populated with a
+// CommitComment encompassing the given message. The Credentials of the returned
+// Commit will _not_ be filled in.
+func (r *Repo) NewCommitComment(msg string) (Commit, error) {
+	cc := CommitComment{Message: msg}
+	var err error
+	if cc.MessageHash, err = cc.Hash(nil, nil); err != nil {
+		return Commit{}, fmt.Errorf("calculating comment hash: %w", err)
+	}
+	return Commit{Comment: &cc}, nil
+}
+
+// MessageHead implements the method for the CommitInterface interface.
+func (cc CommitComment) MessageHead(common CommitCommon) (string, error) {
+	msgAbbrev := abbrevCommitMessage(cc.Message)
+	credAccounts := strings.Join(common.credAccountIDs(), ", ")
+	return fmt.Sprintf("Comment by %s: %s", credAccounts, msgAbbrev), nil
+}
+
+// Hash implements the method for the CommitInterface.
+func (cc CommitComment) Hash(_, _ *object.Tree) ([]byte, error) {
+	return genCommentHash(nil, cc.Message), nil
+}
+
+// GetHash implements the method for the CommitInterface.
+func (cc CommitComment) GetHash() []byte {
+	return cc.MessageHash
+}
diff --git a/change_hash.go b/hash.go
similarity index 76%
rename from change_hash.go
rename to hash.go
index 8c4feb0..d969242 100644
--- a/change_hash.go
+++ b/hash.go
@@ -31,6 +31,12 @@ func newHashHelper(h hash.Hash) *hashHelper {
 	return s
 }
 
+func (s *hashHelper) sum(prefix []byte) []byte {
+	out := make([]byte, len(prefix), len(prefix)+s.Hash.Size())
+	copy(out, prefix)
+	return s.Hash.Sum(out)
+}
+
 func (s *hashHelper) writeUint(i uint64) {
 	n := binary.PutUvarint(s.varintBuf, i)
 	if _, err := s.Write(s.varintBuf[:n]); err != nil {
@@ -64,12 +70,22 @@ func (s *hashHelper) writeTreeDiff(from, to *object.Tree) {
 
 }
 
-var changeHashVersion = []byte{0}
+var (
+	changeHashVersion  = []byte{0}
+	commentHashVersion = []byte{0}
+)
 
 // if h is nil it then defaultHashHelperAlgo will be used
 func genChangeHash(h hash.Hash, msg string, from, to *object.Tree) []byte {
 	s := newHashHelper(h)
 	s.writeStr(msg)
 	s.writeTreeDiff(from, to)
-	return s.Sum(changeHashVersion)
+	return s.sum(changeHashVersion)
+}
+
+// if h is nil it then defaultHashHelperAlgo will be used
+func genCommentHash(h hash.Hash, comment string) []byte {
+	s := newHashHelper(h)
+	s.writeStr(comment)
+	return s.sum(commentHashVersion)
 }
diff --git a/typeobj/typeobj.go b/typeobj/typeobj.go
index fed9225..debe79a 100644
--- a/typeobj/typeobj.go
+++ b/typeobj/typeobj.go
@@ -124,7 +124,7 @@ func element(val reflect.Value) (reflect.Value, string, []int, error) {
 		}
 	}
 
-	if fieldVal.IsZero() {
+	if !fieldVal.IsValid() {
 		return reflect.Value{}, "", nil, errors.New(`no non-zero fields tagged with "type"`)
 	}
 	return fieldVal, typeTag, nonTypeFields, nil