Thank you for using Maple Primes, and thank you for bringing this issue to our attention. I have informed our Maple T.A. developers of this bug, and it should be fixed in an upcoming update.
In the meantime, I can suggest a temporary fix. In T.A. 2016 questions, you have the option to click the "Source" button, and manually manipulate the HTML and CSS source code. By adding the following "style sheet", you can adjust the padding and spacing manually. To do so, just create a table the way you normally would, click the "Source" button, and then copy in this style sheet above it. Once you are done click "Source" again to view your new sheet.
padding: 10px; /* individual cell padding*/
border-spacing: 10px; /* full table cell spacing */
Please feel free to adjust the pixels in the td field "padding" and the table field "border-spacing" to adjust your table's look and feel.
While I cannot speak for what will happen once the developers have fixed this bug, this temporary fix should help. Please note that it would be good to check the appearance of this question after future updates to ensure it is appearing as expected.
Additionally, if you would like to have a bug looked at or addressed in the future, please contact Maplesoft Technical Support directly by emailing email@example.com.
Maplesoft Technical Support