When are speakers considered Hi-Fi and not Mid-Fi???

High fidelity to what in relation to which source? The recorded analog or digital source or the real musician playing which anyway did not exist in an absolute sense acoustically because each location of the listener will give rise to different timbre experience and in relation which very different room or hall...

High fidelity is a marketing term...Not a scientific one...To justify and qualify speakers, amplifiers and dac and recording device as microphones design or reel magnetophone design etc...

Before the gear components and even before the recording engineers trade-off, there is the real violin or piano or chorus playing in a small chuch or in a very small hall or in very big one with each one displaying  his own acoustic properties...

Recording that is an ART  with all different trade-off possibilities for the recording engineer who will decide to pick one set of these and recording that choice on vinyl or cd is not  so much "high-fidelity", it is an optimal fidelity, which we will listen to in some room/speakers relation optimally or not...

High fidelity is a concept in marketing gear electronical design not in acoustic, except to speak about the necessary listener impression...

No recording sound the same in one room /system and in another one...

Acoustic basic knowledge is the ground for optimal experience, not the price tag of products who exhibit yes a dinminushing returns relatively low treshold...

One word:  Thiel

"I can hear music...."

https://music.youtube.com/watch?v=y0ZGnwVfX4o

Stupid argument. Who cares what anyone says. I think it is fair to day what is garbage though. You know it when you see it. Crosley anyone?

The Best Buy haters should differentiate between ones that have a Magnolia department and ones that lump whatever stereo equipment they happen to have with the regular stuff. The Best Buys I've been to have Magnolias, and always have at least one guy who knows about 2 channel audio and a very nicely designed demo room. Maybe not turntable experts since they don't sell many of them, but they do carry them. I wouldn't want them to set one up though.  

They carry McIntosh, KEF, Rega, Rotel, B&W and maybe some other manufacturers that are financially strong companies that can afford to give Best Buy a deal on outfitting these Magnolia stores with demo equipment. 

Interestingly enough, you can usually get a better deal at a mom and pop (usually Pop) stereo store that typically has worse return policies. Except when there is a close out at Best Buy when I expect them to blow out their demo equipment.

I fully agree with @2psyop it’s all relative and a matter of your personal perspective. And keep in mind that much of what is dismissed as “mid-fi” on this and other forums produces better stereo sound than what 99% of the population has ever heard. 

It takes exposure to "quality" "properly set up" systems to be able to build a point of reference. If someone doesn't have the practice or trained ear it kind of becomes a series of judgements on top of marketing hype (or always is). 

After experience comes preference, and once you find your preference people will either agree or disagree with you. If every audiophile listened to 100 systems and rated them for 20 characteristics you'd have some people start picking apart the time of day and the power grid conditions.

There's no simple answer- Miller would argue he had hi-fi and the majority of people told him it was low-fi.