As of Firefox 129 I intend to turn Float16Array on by default. It has been developed behind the preference `javascript.options.experimental.float16array`. The proposal is currently at Stage 3 of the TC39 process. It has been implemented in V8 (https://issues.chromium.org/issues/42203953) but is not yet started in JSC (https://bugs.webkit.org/show_bug.cgi?id=257022).
Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1903329