Might you also be interested in this other thread, on a proposal for a restricted subset of pipe syntax as an alternative to CSV?
Also talks about tables in
http://talk.commonmark.org/t/tables-in-pure-markdown/81/81
An interesting approach to multi line in http://justatheory.com/computers/markup/markdown-table-rfc.html is how PostgreSQL uses the : character: ( Talk in: Madoko - microsoft research's markdown editor )
This is how PostgreSQL renders tables, with multiline cells:
id | name | description | price
------+-------------+------------------------------+--------
1 | gizmo | Takes care of the doohickies | 1.99
2 | doodad | Collects *gizmos* | 23.80
10 | dojigger | Handles: | 102.98
: : * gizmos :
: : * doodads :
: : * thingamobobs :
1024 | thingamabob | Self-explanatory, no? | 0.99
Which might be a better and simpler way to approach this issue, than how your are suggesting at the moment.