Just as I suspected, it was trivial to hack
another parameter onto std.format.doFormat,
to optionally make it ignore any percentages.

And then it's not that hard to implement
std.stdio.write and std.stdio.writeln,
which work the same - but without "format"!

> import std.stdio;
> 
> void main()
> {
>    writef("*** Hall\u00e5, ");
>    writefln("V\u00e4rlden! ***");
>    write("%%% Hall\u00e5, ");
>    writeln("V\u00e4rlden! %%%");
> 
>    writefln("%d%%",100);
>    writeln(100,"%");
> }

Full patch against DMD 0.112 is attached.
Tested with GDC 0.10, without problems...
(well, except the usual line-ending ones)

--anders