The issue is that the table code is an addon - one that isn't supported by the editor/xenforo software by default.
So if you're working with a post with tables in it, you need to press the icon at the right end of the toolbar 'use BB code editor'.
To get things in the middle - apply the CENTRE tag to the outside block only, use CENTER if you want to centre text within it. Avoid using custom fonts with the table - especially ones applied outside the cell level, as that messes things up (seems to be the main reason for all the code duplication you were seeing).
And editing posts seems to ruin tables, so I suggest saving out the initial codes you're going to use before posting, and then copy them in again after clicking that BB code editor button.
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I will look into other alternatives, so if people could explain what things they try to achieve in posts that would be nice.
So if you're working with a post with tables in it, you need to press the icon at the right end of the toolbar 'use BB code editor'.
To get things in the middle - apply the CENTRE tag to the outside block only, use CENTER if you want to centre text within it. Avoid using custom fonts with the table - especially ones applied outside the cell level, as that messes things up (seems to be the main reason for all the code duplication you were seeing).
And editing posts seems to ruin tables, so I suggest saving out the initial codes you're going to use before posting, and then copy them in again after clicking that BB code editor button.
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I will look into other alternatives, so if people could explain what things they try to achieve in posts that would be nice.