I'm trying to find the reference articles, but when I go to Homepage>Features>Armor/AFV, I do not see the yellow 'CAT' box or the white 'Reference' link.

I have been able to access through the link in the 'Best SdKfz251' thread, but I can't get to it directly. Have I got my preferences set incorrectly?

I did a bit of research and digging and was able to reproduce what you are seeing.
I think this is a bug in the system or a feature that Jim is/will work on.

Normally the way I would get to the link you are talking about is to go to "feaures/armor/View All" . This displays a spreadsheet type view and you can sort them by the column headers.
Unfortunately teh Cat isn't a column header.

Thanks. It's not hugely annoying as I can work around it, I'm just glad it wasn't me pulling a DUH moment

Nope - not you - I hate when that happens to me. Sometimes it's nice to know you're not alone.