There is a possibility of showing suggested tags after the body of a question is filled in. These suggestions are based on the body of the question. More details can be found in these posts:
I will quote part of one of the answers, which gives a reasonable summary.
- It uses similar-to-Bayesian reasoning on the text from the title and body of a post
- It has been trained on older questions
- A minimum of around 20k questions are required for accurate results
- There is no substitute for material to learn from, so it can't be rolled out to all sites
If I understand this correctly, this feature is used on Stack Overflow.1 (In one of the post you can see also a screenshot.) But it can be added to any site which has sufficiently many old questions for training the algorithm. (Ideally, most of the questions should be correctly tagged.)
Still, it seems that some non-trivial work is involved when such a feature is added to a site.
Question. Do you think feature like would be useful on Mathematics Stack Exchange? Should we request Stack Exchange staff to add the feature also to our site?
1 Based on the comments on one of the linked posts it seems that this was implemented on SO at some point in 2013. I am not really sure whether this feature is implemented also on some other sites.)