Timestamped Comments is a new feature which will be available with vtiger 5.2 version (upcoming version).
This feature allows you to add comments to records in Leads, Accounts, Contacts, Projects & Project Tasks modules.
You can add a comment from the respective record or create a new comment from the comments module and relate it to the intended record.
The comments added are timestamped which lets you track when a comment was added and by whom.
You can see a short demo below.
PS : This video is for vtiger 5.2 VB2, we recommend users not use validation build in their production environment.