What survives the round trip when data is pasted in
Pasted data does not need to say what it is. The جدول ساز tries comma, semicolon, tab and pipe as the delimiter and keeps whichever produces the most consistent number of columns across every row, which is why a European export using semicolons or a tab-separated file loads without anyone telling it which one it is looking at.
Quoted fields are parsed properly during that process, so a cell that legitimately contains the delimiter — a comma inside an address, for instance — survives as one cell instead of splitting into two. When a row loads with the wrong number of columns, the usual cause is the opposite case: that character sitting inside a cell unquoted, which the detection has no way to tell apart from a genuine column break.
What breaks a Markdown table after the fact
A pipe character ends a cell in Markdown’s table syntax unless it is escaped, so the export escapes it automatically on the way out. A table that renders broken after leaving here has almost always been hand-edited afterwards, with a pipe typed back in raw.
Two Markdown outputs, rendering identically
Aligned columns and compact columns produce the exact same table wherever Markdown is rendered — the padding is purely for a person reading the raw source file. Compact is the better choice for anything going into version control, because re-aligning every column after a single edit turns a one-line change into a diff touching the whole table.
Where Markdown stops and HTML has to take over
Markdown tables have no way to span or nest: no colspan, no rowspan, no table inside a cell. If the data genuinely needs any of those, HTML is the only one of the four exports that can express it at all, and even then the span attributes have to be added by hand afterwards — the output is the plain grid, not the merge.
Why the header row is not just a cosmetic first line
In the HTML export, header cells carry a scope attribute so a screen reader can announce a cell together with the column heading it belongs to. Turning the header row off produces a grid of plain cells with nothing tying a value to what it means, which is also why a table should hold data rather than being used to position things on a page — the structure it announces to assistive technology has to be real.
Nothing leaves the browser
The grid, the delimiter detection, the parsing and all four exports run entirely client-side, so pasting something you would not want sent anywhere does not send it anywhere.