Created attachment 122227 [details] A Calendar spreadsheet with merged cells I Needed to replace "border-right: 1px solid #1d2f4e" rowspan=5 with "border-bottom: 1px solid #1d2f4e; border-right: 1px solid #1d2f4e" rowspan=5 in the html code to correct this. You can view the resulting html saved as from attached spreadsheet.
I see now that this is the result of the merged cells in the block. The top cell borders are propogated to the merged cell's border. In this case the top cell don't have a bottom border where the intuitive result would be to take the outside border settings of the merged cells. I am now not sure if this is a bug or feature. ;^) This should now be assigned to the way Calc works and not to the export to html where the result is only more clearly visible. I propose to use the borders of the underlying cells for the display format rather than that the top most left cell of the merged cells as opposed to using the contents of the top most left cell of the merged cells.
Needs UX input I believe.
We're replacing our use of the 'ux-advise' component with a keyword: Component -> LibreOffice Add Keyword: needsUXEval [NinjaEdit]
Let's say it's a feature. At least I don't see an issue with the document nor when exporting as HTML. In case you still think the export filter or Calc visualization requires changes, please do a minimum example. PS: Sorry for the long delay in responding. We try to improve.