It's perfectly fine. I understand not everyone is a programmer. ;p
To add more keywords, you would do it like this:
local blacklist = {
"keyword or phrase one",
"two",
"three",
-- and so on and so forth
}
Note the pattern—a keyword should appear between two double quotes, and the string of keyword plus quotes should be followed by a comma. Please write all of your keywords in lowercase—the system will check for any variation of upper and lowercase letters, and requires all keywords in lowercase as a result.
Again, this is a rather easy system to circumvent, but if you're happy with it, it ought to run fine.
Drop this file in /lua/autorun/server/ for it to take effect, by the way. Name it something like "chat_blacklist.lua" (note the file extension).