Comments in Writer

I need make comments like in MS Word - to have the beginning and the end of the commant so that I can mark the text commented; IMHO, now it is only possible to make a comment to a single point in the text. Is there any possibility to do it?

No, at the moment comment mark stands at the end of text.
This feature will be available in LibO 3.7.

That’s planned for LibreOffice 3.7:

Bug 38244 - Enable attaching comments to document text ranges in Writer

LibreOffice 3.7 changes - Writer: Enable attaching comments to document text ranges.

Sample LibO-Dev_3.7.0.0.alpha0+ [2012-08-23]

See also → LibreOffice Writer can now attach comments to text ranges

Addendum: The feature will be available in LibreOffice 4.0 due to the modified → Release Plan.