[stealthytea]

I think that's just a compiler directive used if Kodi was compiled with an older version of taglib. 

Almost right by my understanding, it's a runtime check for which Taglib version is being used (mainly for Linux instalsl where different distro may have different versions of system libs) then the version detected determines the code path taken. 

Ah OK. Thanks for the clarification. 
I updated to the latest stable release of Leia, and my wavs with id3v2 tags are still not recognised. As you mentioned Linux, it might be worth noting that I'm running Kodi on Ubuntu 16.04.6.

Having done a bit of reading up I'm personally going off the idea of including those tags in the files anyway, I'm going to write a cue sheet for each file instead and see how I get on. On initial testing it looks good (though sadly my REM COMMENT values aren't recognised, and cue sheets don't support album art).