code: func (o OAuthSession) Reply(r Replier, comment string) (*Comment, error) {
  	// Build form for POST request.
  	form := url.Values{
  		"api_type": {"json"},
  		"thing_id": {r.replyID()},
  		"text":     {comment},
  	}
  
  	type response struct {
  		JSON struct {
  			Errors [][]string
  			Data   struct {
  				Things []struct {
  					Data map[string]interface{}
  				}
  			}
  		}
  	}
  
  	res := &response{}
  
  	err := o.postBody("https://oauth.reddit.com/api/comment", form, res)
  	if err != nil {
  		return nil, err
  	}
  
  	if len(res.JSON.Errors) != 0 {
  		var msg []string
  		for _, k := range res.JSON.Errors {
  			msg = append(msg, k[1])
  		}
  		return nil, errors.New(strings.Join(msg, ", "))
  	}
  
  	c := makeComment(res.JSON.Data.Things[0].Data)
  
  	return c, nil
  }
docs: // Reply posts a comment as a response to a Submission or Comment using OAuth.