Please don't blindly accept those! Adding missing version tags makes sense, but it's useless if there is no indication in the question or comments on a specific version.
Note that you don't see comments in the review queue. I always open the question in a new tab to see if the suggested edit is the result of a clarifying comment
If there is code involved, you will probably recognize magento-1 or magento2 - then feel free to add these tags. But don't assume 1.9 or 2.1 or whatever. See also: Usage of the magento-1 tag if no version is specified in question
If there is no code involved, some questions can even be answered completeley independent of the version. Not every question needs a version tag.
If the version is unclear from the question but important to answer it, add a comment to ask for the version, instead of adding a tag that might be wrong.