Thread:Project:Support desk/Templates not accepting certain parameters

I'm having templates misbehave when certain types of parameters

I created a simple template, "demo template", containing simply  and nothing else. So it should just echo whatever its first parameter is.

Simple enough?

However, this (and every other template) refuses to render certain types of content: some (but not all - I haven't figured out what the difference is) tables, and images (I have $wgAllowImageTag enabled).

This works as expected:

You see "hello hello" on the page.

Everything seems to be going as planned.

But this:

This just prints " " on the page!

The below just shows, a single curly bracket, on the page:

The below just puts " " on the page:

I am using MediaWiki 1.19.2. The db was started from a backup of an extremely old version of mediawiki, if that means anything.