In the interests of perpetuating this endless flamewar, here's Herb Sutter saying C++ programmers should use auto 'by default'.
(I see my snarky comment there got no reply.)
(I see my snarky comment there got no reply.)
People like him tend to be biased about using auto because they write mostly libraries and generic ones at that (data structures, for instance).
In most code out there you actively avoid templates if possible, so that code is concrete, compiles faster and is easier to debug.
Like Sutter's answer, this point doesn't answer the complaint. People on the anti-auto side say it seriously harms readability, as locals' types are no longer clear at a glance. They aren't asking for a list of reasons why some people favour auto, they're asking for an answer to their readability problem.
Perhaps IDEs could infer types and display them as a superscript. That would keep just about everyone happy. (Perhaps not Vim users.)
LLVM's coding standard though doesn't seem to have anything to say about implicit conversions: https://llvm.org/docs/CodingStandards.html