Created attachment 53700 [details]
Patch for the proposed new message

Calc's behaviour when merging several cells with contents is quite different from other applications, and not obvious to guess. 
In other applications, like gnumeric or Google spreadsheet, the contents of the cell resulting of the merge is the contents of the first cell, while the contents of the others is deleted. When you un-merge the cell, the first cell has its original contents while all the others are empty.
In Calc, you can choose to merge the cells' contents or to use the contents of the first cell and hide the other contents. With the first choice, unmerging the cell gives you a first cell with the merged content and the other cells that are empty ; with the second choice, you get all your cells with their initial contents.

Whether Calc's behaviour should be changed is a tough question that won't be discussed here. The point raised in this bug report is that the warning message issued for this action ("Should the contents of the hidden cells be moved into the first cell?") is quite confusing for the user and technically inaccurate.

I propose the following phrasing instead: 

"Also merge the contents of the cells ? (if not, only the content of the first cell will be shown, the rest will be hidden)"

As I'm no native English speaker, the wording may be sub-optimal, but it was chosen with the following points in mind : 

- Underline the fact that the cells will be merged anyway, but that the question is about *content* merging (hence "Also").
- Allow to keep the same type of dialogue (Yes/No/Cancel).

This should allow a simple correction of STR_MERGE_NOTEMPTY in /core/sc/source/ui/src/globstr.src