I am posting this here because I was not able to create an issue in your issue tracker.
I am able to mark and copy an unaltered table in jira confluence:

However, once I edited the table, e.g. inserted a new value in a cell, I am not able to select and copy it any more:

Insted of the expected blue selection that marks the whole table, only some cells are marked.
Work around: If I save and reopen the article, the selection is working again.
I use Confluence 6.7.2