Yes. The spades didn't provide enough visual impact so we changed to using "█" (█) which is a filled box, but being a unicode character may not be rendered by all browsers on all systems. If you are seeing the number in a box I'd guess your browser/system combination don't render it. :(
There is a suggestion on the table that we allow a user selected character - that works around the problem. If there is a lot of support for the idea then I guess that will happen.