In Libre Office 126.96.36.199 Calc it is impossible to copy complete cells from calc into MS Excel 2010.
If I paste it into Excel it appears nothing! Only if I paste as plain text, the text appears in the cell but no border at all.
Copy from Calc to Calc works normal.
This is a regression to 188.8.131.52
Thanks for reporting that.
Calc and Writer affected when we use Copy from thoses apps and Paste to an external app as Excel, Word, Firefox...
This was previously reported in Bug 74584 - Can no longer copy spreadsheet cells from libreoffice calc to another app like thunderbird and paste as html table.
It's already fixed and will be available in LO 4.2.2
*** This bug has been marked as a duplicate of bug 74584 ***