Randall Munroe of XKCD.com has done a masterful job of summing the situation up, I believe:
|©2018 Randall Munroe, XKCD,com|
"This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License."
Seriously, the only data I could be considered to be keeping is if you leave a comment here, and the fact is I delete most comments I get as spam.
What Google, Blogger, and/or Blogspot (assuming there's a difference, which I doubt) may do with incidental data they scoop up as you surf blogs, I can't say. Ask them.