No, replace does not work here. Happy to backtrack on my previous assertion that it would after having had a play with it. The addition is not held as part of the description so you cannot edit it out. It seems to be using the same routine as is used when editing a single listing with bids, so changes would not be allowed - only additions. It appears as part of the description block as it is added to it as the listing display page is created - but is clearly held separately with no means of getting rid of it.
That makes it seem unsuitable for the purposes the OP is using it for. If you want a piece of text that you can update via Bulk Edit then include a piece of dummy text in the original listing - then you can use Replace to modify it.