Merging and the resulting cleanup is a messy and sometimes long process. Once a group of duplicate profiles is merged, one then has to go through and merge, for example, the duplicate spouses and the duplicate children. Not always possible to do all of it in one sitting.
As far as cleaning up the narrative goes, it depends what's there. Frankly 99% of the time, the original uploaders included nothing beyond the event dates and places. No sources, no narrative.
If I have narrative and sources in my own files, then I'll add them.
I delete references to GEDCOMs and to Ancestry family trees, but leave in-- in a section I create called Contributors-- the wiki-names of those people who uploaded or otherwise entered the pre-merge data.
Here's one example: Thomas Cornell had about 12 duplicates. I finally got through the rest of them tonight.
This merge was complicated because there is disagreement about who his parents were. I conducted research of published records to see what the most current thinking was and added it.
That meant detaching Thomas from all his theorized parents until such time as confirmation is found. (I need to add links to those theoretical parents in the narrative still.)