Multiselect user experience and research reflex

A question was asked to me recently if it was fair to assume users know how to use multiselect keyboard modifiers. This led to a broader conversation about what kind of multiselect was in use here. 

My first impulse was to check the data. In the 2019 article "<select> Your Poison", real life testing was completed to answer the question which multiselect is better?

Notably, `<select multiple>` tested the worst out of four options. Drawing from that article, I lean on one of the following patterns for multiselects: 

• Comma-separated values
• Buttons above combobox

But in the end I agree with the article's original thesis: just use a select element!

Source: "<select> your poison part 2: test all the things" [https://www.24a11y.com/2019/se...]