Good on you to leverage EditorConfig settings. Almost every modern IDE or editor supports it either out of the box or with a plug-in.

I like that there is plenty of room for comments, and the multiline extension is also cool. The backslash almost looks like what I would write on paper if I wanted to sneak something into the previous line :)

This is pretty under-specified...

> A cell starts with | and ends with one or more tabs.

    |one\t|two|three

How many cells is this? Seems like just one, with garbage at the end, since there are no closing tabs after the first cell? Should this line count as a valid row?

> A line that starts with a cell is a row. Any other lines are ignored.

Well, I guess it counts. Either way, how should one encode a value containing a tab followed by a pipe?

We need binary formats. In this era we are capable for it. Throw away the text formats.

According to spec it's nearly impossible to correctly edit files in this format by hand.

> A row with too many cells has the superfluous cells ignored.

Ummm, how do you figure out what row has too many cells? Can all the rows before this one have too few cells?

I hate this kind of format. It's trying to be both a data format for computers and a display format for humans. Much better off just using a tool that can edit CSV files as tables.

Also it doesn't seem to say anything about the header row?

Or we could use the actual characters for this purpose - the FS (file separator), GS (group separator), RS (record separator), and US (unit separator).

ASCII (and through it, Unicode) has these values specifically for this purpose.