Here's some reasoning behind the new character limit for signatures. Once upon a time, signatures were disabled because some people were using them for political pronouncements or other things that did not serve the harmony of FT. A lot of members asked for signatures to be returned.
Talkboard was given the task of coming up with guidelines for signatures. They did so, and you can find them
here. The guidelines say in part:
As a courtesy to members we suggest you follow the these guidelines when creating your signature:
* Use the normal posting font size.
* Limit your signature to two lines.
* Text should comply with our regular posting rules. No all-caps, no alternating caps, etc.
* Do not make your signature too long or obtrusive through overly creative use of punctuation, color, etc.
* Avoid putting your username in your signature as it's already on the top of each of your posts.
Moderators continued to see some signatures well beyond the two line recommendation. Putting a character limit is an attempt to find a low key way of encouraging members to follow the Talkboard recommendation.