I disagree with porn having no place on the Fediverse. A lot of amateur creators started their work on sites like Reddit, and the platform becoming unviable will push them to alternatives like Lemmy.
However I do agree that there should be some gateways to get to that point. Filtering instances/subcommunities that are marked directly as all-NSFW is a good first step (and should've been part of the protocol from day 1).
I also see why the default "filter out all NSFW content" filter is problematic (even though it is enforced by app stores on every mobile platform, sadly). A much better approach is to filter subcommunities and instances that are marked as entirely NSFW. That way e.g. news subcommunities can still post NSFW articles that have a wider reach, without anyone's primary feed getting slammed with porn and gore.
At that quality of MP3 you'd really need either a track that specifically pushes the limits of the codec on technicalities, or a one in a million hearing + high precision monitors.
Albeit FLAC is generally a better option still because it compresses things losslessly, reducing raw file size 50-70% (comparable to MP3 at 128kbps bitrate) and is a royalty-free, meaning it can be freely implemented as a hardware codec.
For example, a bunch of microcontrollers in the ESP32 family have built in FLAC codecs that outperform their MP3 counterparts, meaning a FLAC library can be directly streamed to them, and with the right DAC combo, one can build inexpensive, low power adapters to hook their existing AV systems up to Sonos-style streaming. And with many AV systems supporting bidirectional RS232 (or other serial) communications for controlling the system and querying it's state, you can literally smartify them completely AND provide high quality audio streams to them.