Workflow Update Rows with Username

I have a Comment Table where users can leave comments. The Comment Table automatically adds the name of the user who left the comment ‘Username’. There is a separate table called “Updates” where one specific user is responsible for updating groups of items. Once a certain number of items have been updated on the ‘Updates’ table, I have a workflow that adds a comment to the Comment Table, however, it computes the Username to be me, whereas I want it to leave the name of the user who made the updates. The Action being triggered by the workflow does not allow me to include a formula for the ‘Username’ column and I’m assuming that’s because the Username column is auto computed.

How do I go about adding an expression for this column to be with a certain Username if this action is the source of the comment?

Your table structure is not entirely clear to me but it think a workflow knows who made the change that triggered it as USEREMAIL(). I would suggest to set the column of who updated to USEREMAIL() instead of USERNAME() as a grouped action with whatever else your current action does.