Wikimedia Bugzilla is closed!

Trying to create a table within another table, be it using wikitables or plain
HTML tables, will break the syntax of the outermost table. For example, this code:
{|
|-
| New table:
{|
| Table within a table
|} || This be a new cell
|}

As well as this code:
{|
|-
| New table: <table>
<tr><td> Table within a table</td></tr>
</table> || This be a new cell
|}

Will both render as:
<table>
<tr>
<td>New table:
<table>
<tr>
<td>Table within a table</td>
</tr>
</table>
|| This be a new cell</td>
</tr>
</table>

The || is rendered as plain text, instead of table syntax. However, it will be
rendered correctly if a line break is inserted right after the innermost table:
{|
|-
| New table: <table>
<tr><td> Table within a table</td></tr>
</table>
| This be a new cell
|}

Will render as expected:
<table>
<tr>
<td>New table:
<table>
<tr>
<td>Table within a table</td>
</tr>
</table>
</td>
<td>This be a new cell</td>
</tr>
</table>

This is especially annoying when transcluding templates which have tables
themselves, as one cannot be sure that those templates have line breaks after a
table, and is so forced to insert one.