What MediaWiki is
MediaWiki table markup opens with {| and a class, marks headers with an exclamation mark and rows with |-.
Wikipedia editors and anyone running a MediaWiki install.
What TSV is
TSV is CSV with tabs instead of commas. Because tabs almost never appear inside a value, quoting is rarely needed and the files are easier to read by eye.
Bioinformatics, log processing, and anyone who has copied a block of cells out of a spreadsheet: the clipboard format is TSV.
What changes when you convert MediaWiki to TSV
Both cell styles are read: one cell per line, and several on a line separated by exclamation marks or double pipes, which is the form most Wikipedia tables use. Cell attributes before a single pipe are dropped, since style="text-align:right" is presentation rather than data. Wiki links come through as their display text, so [[France|the French Republic]] arrives as the French Republic, and reference markers are removed.
Pick TSV over CSV when your values contain commas. Pasting the result straight into a spreadsheet fills the cells correctly with no import dialog.
What carries over from MediaWiki to TSV
MediaWiki records 4 things about a table that TSV has no way to hold.
MediaWiki can hold a value that is itself a list or an object. TSV has only flat cells, so nested values are flattened into one cell rather than being spread across columns.
A line break inside a cell ends the row in TSV, so line breaks are replaced rather than carried through.
TSV has no separate idea of a header, so the column names become an ordinary first row and nothing in the file marks them as different from the data.
Anything visual in the MediaWiki - weight, alignment, colour, column widths - has no counterpart in TSV and is dropped. The values are what survives.
The result can be read a record at a time, and appended to by adding to the end of it. That is worth having for a table too large to hold in memory, and it means a TSV file that is cut off part way through still gives you every record before the cut.
The identifier 007 comes out of the TSV as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a TSV file goes wrong.
The quotes around Jonah "Jo" Pryce are doubled, which is how the delimited formats escape a quote in the TSV.