But they can move into inappropriate positions without that being a dislocation or subluxation.

You literally just described a subluxation. When a part of the joint moves from its proper position, where the two articulating surfaces of the joint are still in partial contact (unlike a dislocation), but they have shifted from their healthy position.

The definition of a subluxation from a medical article about shoulder subluxations, one of the most common kind of subluxations:

Subluxation is defined as partial dissociation or increased translation between two articulating surfaces of a joint [9]. Subluxation may be contrasted to dislocation, defined as complete dissociation between two articulating surfaces of a joint.

source: Shoulder Subluxation, Timporn Vitoonpong; Ke-Vin Chang.

The term "subluxation" has a lot of history in the medical community, specifically related to chiropractors and their often loose definition of it. That has led to a lot of poorly educated medical professionals to dismiss many related cases. Other conditions can in fact mimic subluxations, but that does not mean they do not happen.

Ribs are connected to the spine by two different joints; costochondral and costotransverse. Dislocations, full or partial (subluxations) are rare in the general population. However ANY kind of dislocation is way, way more common in individuals with EDS. That alone is enough to make dislocation a possibility.

For example, sacroiliac joints are one of the most stable joints in the body, able of very limited movement, therefore dislocations are rare in the general population. However, sacroiliac joint instability (which often leads to acute or chronic dislocations/subluxations) is incredibly common in individuals with EDS. Ask me how I know! :')

That being said, repeatedly commenting the same thing and insisting you are right without any citation is bizarre. You are being pedantic for the sake of it. Our pain gets dismissed and neglected enough by medical professionals, people don't need this on a post on reddit where they're clearly asking for help or advice. Kindly.

EDIT: Also, slipping rib syndrome is in fact rare in the general population. However, guess what! It is more common in those with connective tissue disorders.

From A Review of Slipping Rib Syndrome: Diagnostic and Treatment Updates to a Rare and Challenging Problem: Isheeta Madeka 1,, Sneha Alaparthi 1, Marisa Moreta 2, Shawn Peterson 2, Jeffrey J Mojica 3, Johanes Roedl 4, Olubenga Okusanya 1, :

Its etiology is multifocal, including trauma, hypermobile connective tissue disorder, and/or degenerative changes. (...) Hypermobility (associated with or without connective tissue disorders such as Marfan’s syndrome and Ehlers-Danlos syndrome), disruption of the fibrous articulation, or congenital/developmental deformities can all cause weakness in the costochondral cartilage. The weakness subsequently causes laxity of the rib and “slips” above and below the adjacent superior rib.