This commit may cause random failures when org-emphasis-regexp-components is changed by user. org-emph-re is calculated according to org-emphasis-regexp-components. Changing org-emphasis-regexp-components can make "(when (looking-at org-emph-re)" in parsers return nil. The emphasised text will still be fontified, but not available in the parsed buffer.
Maybe we need to move the logic for org-emph-re from org.el to org-element.el? Also, there is org-emphasis-alist. It is even defcustom, but ignored by org-element.el. Best, Ihor