When should someone put education credentials after their names? BS, MBA, MFA, JD, PhD etc etc etc when is it acceptable and at what level?

I think a graduate degree or above is appropriate. I put it in my signature block, and that's about it. I also use only the highest degree earned. I think the highest degree trumps the lower degrees, so adding multiple degrees is unnecessary. I suppose an argument can be made if someone has two terminal degrees (like a PhD and JD, or a PhD and MD).

Decided to go hunt for this answer. Check out https://en.wikipedia.org/wiki/Post-nominal_letters.
Basic answer:

In the United States, standard protocol is to place them in this order:
Religious institutes
Theological degrees
Academic degrees
Honorary degrees, honors, decorations
Professional licenses, certifications and affiliations
Retired uniformed service (active duty service brackets the name – e.g., Firefighter John Doe, CFD – and active duty armed services do not display postnominals other than branch of service)[1]

Common practice is to name only the highest degree in a particular discipline (e.g., if one had earned one's BS, MS, and PhD in Biology – even from different schools – as well as an MBA in Management, then the preferred listing would be John Doe, MBA, PhD).

I work in the education field myself and I only have a BAS but who needs to know that? To me it's just those person's in my opinion need this to feel important. It's like some of my co-workers here at work, call them by their first name oh it's Dr., LMBO give me a break lol.

Context is everything. If you are presenting in front of a body of professionals for example, your highest level in that field should be listed for credibility. I co-facilitate a medical awareness class with a nurse, therefore RN is listed after her name on the PowerPoint. I have a co-worker that is a subject matter expert in her discipline, yet she does not feel the necessity to list the fact that she has a Masters degree.

The most common is PhD. Others are less common.

Realistically, only when required by policy or when it is directly related to the subject at hand.

As a public school teacher I forced my student into using proper formal salutation. As a college professor I haven't had to do that. These college students do it naturally. However, the president of our university wants formal proper salutations used i.e. Dr. or professor. As far as correspondences we are required to use masters or doctoral credentials as part of our email signature. I don't recall anyone using baccalaureate degree credentials.

If you're proud of it, which you should be, put it on there. It's an accomplishment, which in turn makes you accomplished.

I would argue that less than a Masters Degree should never be included and that higher should be included only if such a degree is a requirement for the job. For example, for a doctor to put PhD after his or her name makes sense, ditto for JD for a lawyer. A required certification to practice is probably a good idea as well, ie CPA for accountants. But for me to put BA after my name would make me look ridiculous.

There's one profession that every time I meet someone from that vocation they make a point to say "I'm a certified..." While any level of education is a great accomplishment to the individual who holds such credentials, I've always found most define themselves by the title. Like others have said, when the time is appropriate the credentials are beneficial.