I just asked this question myself (was duped and is what lead me here).
Another workaround:
On my question, animuson commented:
If you want to see the tag excerpt, you can just click on the tag to
convert it to text, and the tag suggestion box will pop up below the
input box
Having tested this, I'll add:
If you then click elsewhere on the tag bar it turns from text to a tag again.
This works ok, and am glad of the info, but it is only a workaround and not a good UI function.
I don't need to untag, I need to see excerpt to decide if to untag.
I also don't need all "similar" tags which this workaround shows as it brings up the selection box. That is different, and is there for other specific reasons and uses.
Workarounds are not specifically designed, so we end up with adverse effects.
Or we lose them, as using things they were not designed for is not considered in site changes (like the workaround in ShadowWizard's answer).
It was stated there is no reason for this not to be implemented, so just wondering if there is any update to when this might be done?
I know your folks are always busy, and this might be low down on your list still.
But, while it can be argued this missing functionality is no big issue, making sure questions have the right tags is important, and the proposed functionality would make that easier, quicker, and less "hacky".
I would certainly use tag bubbles in edits on a daily basis :)