The "non-curly-brace" form of jAlbum variables was deprecated quite a long time ago, but it appears that David didn't finally disable them until jAlbum 17 or 17.1. They still work in jAlbum 16.2, which actually surprised me!
There's only one remaining place where the "non-curly-brace" style not only still works, but actually has to be used, and that's when you're using variables in one of the image filters - a rare use-case, to be sure.
Thanks for that additional comment.The most recent album I made and posted was on Dec 1st, and apparently made with 17.0 (the credit line just shows 17). I must have skipped 17.1 and didn't encounter the "problem" until I updated to 17.1.3. Now that I am aware, it is no problem for future albums, but I'll have to be careful about changing it if I remake an older album.
That change in the jAlbum core is probably going to catch a lot of "tinkerers" off-guard, since until now, jAlbum has been tolerant about using the old-style variables.
It was like the release when David finally tightened up the scripting tags, so that all the <ja:if> and <ja:else> tags had to have matching closing tags, or it would crash with an error. That dredged up all manner of sloppiness in our old code.