Learn English – What does it mean when too much formality can appear menacing

Regarding "do the needful", Wikipedia has an article on the subject. It indicates that it was more common in English in the past. I don't think it is grammatically wrong; it is just more a matter of idiom in US/UK English. There we would more likely say "do what is necessary" or "do whatever it takes".

The same is true with pluck the flowers. It is grammatically fine; it is just not the idiom.

In regards to prepone, this is an Indian coining, and I personally think it is a great word. However, it has not made its way to Europe and the US. Frankly, I think it is our loss.

Indian English is a perfectly legitimate dialect of English and need in no way feel inferior to the mother country's version. On the contrary, India has been an abundant supplier of words and phrases to British English, and we owe the Indians a debt of gratitude in that respect. "Pluck the flowers" might be a little odd sounding to the British or American ear, but Americans "could care less", while Brits "couldn't care less", and Americans don't get too pissed, and Brits don't get too pissed off at each other about the differences.

As we English speakers like to say: vive la différence.

In my experinece you run into people and trouble:

I ran into Betty at the store today. I haven't seen her since college!
I ran into your co-worker Bob today.
Sorry I'm late; I ran into heavy traffic.

You come across objects:

I was cleaning up the kitchen and came across that phone bill you lost.
I was looking up (something) in the encylopedia and came across this interesting tidbit.

I'm not sure I'd use either when talking about a grammar error in a blog; I'd be more likely to say I found or noticed it. I don't know why that is.