Thank you to everyone for your feedback on this issue.
While we can see the value of vertical alignment in table cells, we are striving to provide the most delightful and usable editor for the most customers. Vertical alignment, while "simple" from a technical standpoint, vertical-align: middle, it adds interface complexity for everyone whether they need the feature or not, which is why we have not prioritised it to date.
This feature isn't on our immediate the roadmap, however it hasn't been ruled out for inclusion at some point in the future. It is clear that this type of alignment would be a useful feature, which is why the suggestion hasn't been closed.
— Phil Oye, PM, Atlassian editor team