Is use of the symbol ® to be recommended ?
In principle, yes, but use must be in keeping with the facts, i.e. where geographically the trademark is used in conjunction with the symbol ® a corresponding trademark registration must have been obtained.

Use of the symbol ® must correspond to the reality and be true from all points of view.

If for example the symbol ® was used in conjunction with a trademark on a product not covered by a formal trademark registration or if the trademark with the symbol ® was used on products or advertisings in a jurisdiction where no registered trademark has been obtained, this might have undesired legal consequences.