Forms should have a label per https://dequeuniversity.com/rules/axe/4.10/link-select.
This is not the case for the <select> element above the comment field which has "Add Action..." as its first option which is created via id(new AphrontFormSelectControl()) in PhabricatorApplicationTransactionCommentView. Add an aria-label attribute for screenreader use.

Ref T16072

• While logged in, go to http://phorge.localhost/T1 or http://phorge.localhost/D1 or http://phorge.localhost/P1
• Inspect the <select> element above the comment field (which has "Add Action..." as its first option) with and without this patch.
• Optionally, run an Accessibility check in Chromium Lighthouse.