I think the objection to saying “I read somewhere” is that it can be seen as an attempt, even if unintentional, to give a statement more credulity than it deserves.  It shifts the burden for proving authenticity to an unnamed author “somewhere”.

Don’t upset the tutters.  Bad move.

Credulity?

(Runs and hides).

Tut!  (Suddenly I’m hearing Steve Martin in my head...)

Tut me no tuts.

Credibility, of course.  Just tusting.

No offense taken, bayard. I shouldn’t have answered so testily, but i was sober at the time.