Make the default position of accordion chevrons on the left side of the title

[mbgower]

We have data from low vision user studies showing reduced usability due to the distance between the chevron indicator and the label. By their nature, right-side chevrons will normally have a greater distance; on implementations across many columns, the space can be significant.

In our user testing, several sighted users missed the accordion indicator, and did not understand headings were actionable until exploration with a mouse. When a user uses any form of magnification, the result is that the cue for an accordion may be missed since the chevron is not even displaying within the viewport. The lack of any other contrasting visual cue for an accordion increases lack of recognition of the component.
For accessibility, we recommend aligning the chevron on the left. Designers viewing this guidance have asked why the default is on the right if this is our recommendation.
At the least, I recommend you better document the accessibility case for left-aligned in Usage, and the scenarios under which right-aligned chevrons are preferred and why.

Some other points about this:

• one of the arguments for right aligned is that they take up less space, but in most circumstances this not the case; both the text and the accordion need to fit in the viewport without horizontal scrolling
• some have argued that left positioned chevrons cause text alignment problems. If the accordion title is inset, and the text of expanded accordion matches this inset, it may make it easier for users to understand where accordion text ends and a new accordion begins; this may be worth some user research.
• on the same topic of text alignment, on the Usage page, it appears that the right-aligned chevrons are located outside the text area, as shown below. If this is the case, an option is to locate the left positioned chevrons outside the text area on the other side
  
• note that such chevrons in the gutter are implemented on IBM's internal pages.
• there are situations where both left and right positioned accordions may be more appropriate. I am not advocating eliminating the right positioned chevrons, but I am arguing that left positioned are defendable for improved experience for many users, and should be considered as Carbon's default, not exception.
• The ARIA Authoring Practices demo page unintentionally includes both. See the note preceding the demo as well as the example.