Created attachment 389685 [details] simple table example there is no clear and unambiguous description for the dx Attribute in the case where the XML character data within the 'tspan' element is null or space. There is currently a difference in rendering between UAs, and errata filed as per URL above. The current description appears to be here: http://www.w3.org/TR/SVG11/text.html#TSpanElement but afaict this possibility is not described. In my view whether the character data within the 'tspan' element is null or space it should be respected. the rationale being that whereas in the attached example it is probable that there is a primary key column it is easy to conceive circumstances where a key would not be appropriate, or the key data may currently be unavailable, but one wishes to display the available data.
<tspan x='30' dy='2.5em' font-weight='bold' fill='crimson' text-anchor='start'></tspan> dy should be and is ignored here so no bug. See Ken Stacey's explanation in the w3c mailing list for more details.
Please open another bug on the <tspan dx="<value>"> </tspan> issue excluding the invalid <tspan>dx="<value>"></tspan> part.