The original poster's "tagline" was not a tagline at all but an advertisement and voted down by the community as such -- which I completely agree with. That said, even if that weren't the case, our official policy on signatures is on the /behavior Help Center article on each site:
Do not use signature, taglines, or greetings.
Every post you make is already “signed” with your standard user card, which links directly back to your user page. If you use an additional signature or tagline, it will be removed to reduce noise in the questions and answers.
Your user page belongs to you — fill it with information about your interests, links to stuff you’ve worked on, or whatever else you like!
We don't want to clutter up question pages with a lot of redundant signature blocks and taglines and so forth. While these are common on forums, questions and answers on Stack Exchange should contain only relevant content.
Please use your built in profile, avatar, and username as your signature; that's what they are there for, and every post you make is already "signed" this way!
We do of course encourage people to put lots of interesting information about themselves on their user page, and we try to drive interested people there so they can learn who you are and what you're about. Self-promotion is fine on your user page.
If you see posts that include signatures, please EDIT out the signature blocks - along with any other needed edits. Stack Overflow is collaboratively edited! You can help keep the quality of posts high by keeping the noise level low. If the user reverts these edits, then flag for moderator attention.