Well now, if you're talking about the "old days", you'll remember the absolutely enormous gifs some people used as sigs which were, as you rightly say extremely annoying and took up huge amounts of space especially as some of the users only managed "lol", "roflmao" "yhm" and many other forum acronyms as their comments which, when used multiple times by the same people totally disrupted a thread.

Some of the gifs were true works of art but shouldn't have been used as sigs for the reasons above.

The current use of fonts, sizes and colours are only expressions of individuality or as a reflection of the comment, otherwise the colours on this thread are often relevant to the word or meaning of the word.