Given a simple table such as
| Name | Age |
|-------+-----|
| John | 20 |
| Peter | 25 |
|-------+-----|
place the cursor in the cell containing 'Age', insert two columns pressing 'M-S-right' each time and, immediately after that, delete two columns with "M-S-left". One would expect the table to return to its original state, but is doesn't. In reality the table becomes
| | Age |
|---+-----|
| | 20 |
| | 25 |
|---+-----|
because the second deletion actually kills the column labeled "Name".
Contrast this with the behaviour of inserting and deleting characters in text-mode and you will see that the above behaviour is counter intuitive.
I believe this is due to the fact that 'M-S-right' inserts a column at the cursor, placing the cursor within the inserted column, while, after deletion, the cursor is placed in the column to the LEFT of the deleted column (except after deleting the leftmost column).
A possible solution is to place the column to the RIGHT of the deleted column after deletion (except after deleting the rightmost column).
Best wishes,