I noticed that, under some, unknown to me circumstances, some functions, whether from base R (for example, gc()), or from external packages (for example, getCurlHandle() from RCurl), still produce output, even after explicitly disabling it via verbose = FALSE. I am curious about reasons for such behavior. The only workaround I found on SO is the recommendation to call invisible(), but for me it worked only for gc(), but not for getCurlHandle(). Would appreciate any comments and answers.
While preparing a reproducible example, I figured this out. The source of the questionable output was not getCurlHandle(). It has been producing by another (next) function: curlSetOpt(). I took care of disabling its output by using invisible().
It was really not bad, comparing with the effort I've made for figuring out my previous R and RCurl problem. But, it is always fun and educational.