Normally, when I browse a site in desktop mode on my iPhone, I can tap a comment and the upvote and flag options will appear:
However, this doesn't work when reviewing from mobile. I can tap or long-press whatever I want, but the upvote/flag options won't appear.
This is not really a duplicate of Allow voting on comments from Review interface; that's simply a feature-request which has never been updated to status-completed (so I do understand the close votes). For proof, see the screenshot below:
(and flagging is possible as well, by the way)