I assume that the main reason is because it would just make one step easier for people who like to be obnoxious.

Null'd my vote.

I think what he means by that is people would be abusing using all different colors and this would cause more spam to me as well. And as SCXiao just did above, there is some font where you cannot even see the font at all.

I'm going to have to say No as well.

colors can look a lot different depending on the board style you are using (sometimes they will blend right in, or contrast nicely, etc)

it's just a lot easier if everyone uses normal colored fonts for discussions, and colored ones for trying to point things out, or make things more noticeable

as SCXiao showed above, people could use transparent, or near transparent hex codes, or obnoxious colors like light pinks, yellows and others

What I'm trying to get across is that, like you said, it's convenient - and will be more convenient for people to use it negatively/abuse it, and encourage others to as well.
I'm not saying it isn't a nice feature, it would be great to be able to personalize posts like that, but it's too much of a giveaway to those who have no respect.

To help you, there is an addon for firefox called clippings - you could use that, and then put your specified bold/color into a script for that and it is just as easy as this suggestion would be.