If I create a table in a writer document, and assign that table a table style, then customise the formatting of some entries (say, highlighting an entry with bold in one table cell), that custom formatting is lost when rows are added to or deleted from the table.

This is unexpected behaviour and on a larger table can result in the loss of significant amounts of custom formatting. FOr some documents and workflows it is not feasible to keep all tables in a plain format and do the formatting at the end as iterative changes can be required.

The expected behaviour would not be to reapply formatting to the table, just to the newly added rows.