people can just use any other customization option to create insensitive messages, that's not a problem unique to pronouns. i think the good would greatly outweigh the bad, and it's not possible for the site to keep up with every possible pronoun that a person would like (and most users will not want to go through the effort of making a feature request, especially if it's something personal like pronouns)
if its REALLY a problem, add some limitations, i.e. plaintext characters only, no spaces (only / ) and a reasonable character limit
