There's a difference in the colour of the tags. Here's a screen grab from the "legend" on the tags page:
{required-tag}has RGB = (68,68,68){tag}has RGB = (85,85,85)
However, this is too close to discern when both are bold. For example, on Meta.TeX.SE one is required to have one of the four tags bug, feature-request, discussion or support which are one-boxed in bold. With the current setup all tags are bold:
I enjoy the feature of having certain tags represent something other than the usual content. For example, the red colour of the moderator-only tags: status-completed, featured, status-bydesign, status-deferred, status-planned, status-reproduced, status-review, status-declined and status-norepro. This is lost though with the addition of making all tags bold.