I also agree with both billericky and Richard Craig. Aside from professionalism and improving writing skills, it is also about making the effort to communicate properly with everyone in this community. For me, I feel that by making the time and effort to construct my comments and responses as best as I possibly can and using correct grammar as much as possible (I am not perfect, so I need the practice also) I am also extending courtesy to fellow hubbers and the hub pages community with that effort.
Another thing, I consider chat language quite informal and something best reserved for close friends. While we may interact with each other here quite closely, to some extent a number of us are not personally acquainted, so I find it presumptuous to be very informal by using chat language. For me, it is a way of also showing respect for my fellow hubbers.
Of course, I understand the use of chat language, sometimes the medium you use has limited amount of characters to use to get your message across so abbreviating it makes sense and is practical. But here in hub pages there is no character limit in our responses and comments so I find no need to abbreviate messages and feel that i should make the effort for the reasons I stated in the preceding paragraphs. This is just my opinion by the way, I am not saying this is how it should be.