While editing tags I noticed that some don't show the beginning of the excerpt when viewed on the tags page. For example "banns" is missing the first five words when shown on the tags listings (hovering over it gives the full content).
Many (most) other tags do have all words displayed on that page, for example Alsace. It doesn't seem to be related to the length of the excerpt (those are about the same length). So what causes it? Most of the time, it's because the first word repeats the tag, but not always, there's something else.
In some cases, it can make the resulting description over-terse, such as for "alien" or "gendex".
Alien contains:
A mostly American term for somebody who is not a citizen of the country.
shows:
not a citizen of the country.
Gendex contains:
Contraction of GENealogical inDEX used to describe a specification for data exchange.
shows:
describe a specification for data exchange.
(it's the same on this meta site, click on the Tags link here and see the way the "dscussion" tag is missing the first few words until hovered over, yet the "bug" tag is OK).
Discussion contains:
The question you're asking is designed to solicit opinions or best-practices on a particular topic, with the goal of reaching community consensus.
shows:
designed to solicit opinions or best-practices on a particular topic, with the goal of reaching community consensus.