What mean "noisy"?
Why is having four choices too many? It makes flagging simpler, if the flagger cannot choose between the four descriptions then there is a fifth venue available, other...
How long does it take to read these descriptions, how much "wasted" space does it occupy? I like the descriptors, they're written in plain English which anyone can understand. Remember, not everyone is an English native speaker, giving non-native speakers a range of choices is being helpful. Moreover, the term noisy may not be clear, if you have to provide a detailed definition of noisy and include "chatty"; "unconstructive" and "obsolete""chatty"; "unconstructive" and "obsolete" you might as well keep the original options!
Asking someone whose level of English is basic to write the reason for flagging a comment could be off-putting and cause unnecessary headaches. But if I had to streamline the options, I would suggest merging "unconstructive" and "chatty" under one name: "unproductive".