Acknowledgment to a referee of a different journal who previously rejected an article I received a referee report on one of my articles. The report is amazing and gives me wonderful directions to improve my work however he rejected the article. Now I rewrote the article considering his comments and I am going to submit the article to a different journal. I would like to thank him or to say this version is thanks to this referee. Is this regular and how to say it?
Yes, it's certainly regular: acknowledgements to referees are not uncommon. I'd formulate the acknowledgement in the following way or similarly:


  The author would like to thank the anonymous referee who provided
  useful and detailed comments on a previous/earlier version of the manuscript.


The qualifier earlier should be enough to disambiguate. In addition, once the paper is published, you can also write an email to the editor of the journal where you had once submitted the manuscript, asking them to pass your acknowledgement to the referee.