Steps to reproduce:
1. type a few random stuff in a column
2. select those cells
3. click on the toolbar button that does sorting (A-Z or Z-A, it doesn't matter)
4. wonder why the first cell remained the same
LO thinks that the first entry is a column label. Always. It's impossible to change this. When you use "Data/Sort..." from the menu, it also defaults to column labels, but thankfully it can be disabled.
*** This bug has been marked as a duplicate of bug 91305 ***