Export scripts create external text files - so they do not change anything in the tags.
See the HowTo-FAQs on how to create a new action:
To assign a value to a field, use an action of the type "Format value", in this case for COMMENT:
Yet, I find it strange to write such a statement to a field - wouldn't it be a better step to filter for such files and then run an action or something to solve the problem? Because, I mean, what will you do with the information in the comment?
This filter would show you the files with longer titles: "$ifgreater($len(%title%),30,yes,no)" IS yes