On Google, the first result for "blur image text" is Tool to quickly hide/blur/redact text in screenshot? on Ask Different. The question has over 100,000 views.
The accepted answer recommends using Skitch. Back when the question was originally asked, Skitch was a good platform‑neutral solution. Unfortunately, Skitch for Windows was discontinued in December 2015, meaning it is now a MacOS specific solution.
The equivalent question for Windows on Super User only has a bit over 10,000 views. While revising the question to be more on topic, I renamed the question from "What tool can be used to blur images?" to "How can I blur text in an image in Windows?", hoping that it could improve Search Engine Optimization (SEO).
While SEO wasn't the only reason I renamed the question, (the old title was off-topic as a software recommendation), it made me wonder whether editing a question's title to improve SEO is typically an acceptable thing to do.