A lot of prof and people in mathematics(and other fields too) have their own webpages. Now there can be a lot of questions that relate to academic blogging such as "Should there be a like button in your academic webpage or blog?"
I think questions about academic websites are solidly on-topic. In fact, we have several highly up-voted questions on this topic, with good answers:
- Should I host my academic website under my institution domain or under a domain of my own ?
- What contents should I put on my academic website?
The answers highlight significant differences between academic websites and other personal websites. For example, it is very common for your institution to host your website, and there are cultural expectations about what sort of information you should and should not include.