I think the current chat and social system in STO needs improvement and expansion.
The reason why is because it is very hard for people of similar interests to find each other and communicate ingame, and most people aside from small groups rely on the ingame social system to perform these thing. PvPers can't coordinate to play matches with/against specific people on both sides, roleplayers don't know who's RPing and who isn't, and casual players don't know who's looking for a team. Simply put, the chat and social system right now is an obstacle rather than a tool.
I have a few suggestions as to how to better improve the system in place right now.
1) Expand Public Channels
Many players from other MMOs are used to having access to a lot of public channels in order to communicate with each other for various reasons. Currently, the only channels people can communicate with each other is local, zone, and 5 player channels. As strange as this may sound to a new player, these are not enough avenues for player communication.
I suggest that there should be additional public channels for other people to communicate to each other with. For example, a public PvP channel will allow both dedicated and casual Federation and Klingon players to coordinate matches better against each other, as well as have a ingame venue to discuss PvP tactics, PvP Fleets, and personal superiority over each other in an easy and obvious ingame channel. Starting up a new player channel for such things is impractical and cumbersome, because players cannot search for such channels and may not have the room for another channel. If players had an easy and obvious avenue like "zone chat" to chat through based on generalized interests, then communication between those players would go much more smoothly and productively.
These channels, like "zone chat", would be public and self regulating, and not like private player channels, just to clarify.
To finish this point, here is a list of the new public channels I'd suggest STO having in addition to "Zone".
Remember, while some people may not use them all, everyone enjoys having the OPTION to use them.
2) Double the Private Chat Channel Limit
Yes, make the channel limit 10.
Considering the fact that STO shares it's chat server with CO, many players who play both are severely limited as to player channels. Fleets/SG's might have public channels for their guilds, or they might have special interest channels they want to be a part of in both games. Five channels for both games is very limiting and frustrating. 10 Channels on the other hand will allow a great amount of flexibility while keeping a cap to ensure the chat server does not get overloaded.
Simply put in this case, more is better.
3) Special Interest Player Color Labels in Chat
A MMO attracts many players with special interests. Of these, PvP and Roleplay are the two major special interests, and players will often seek out those with similar interests. Currently, as we are all one big happy server with multiple instances, these special interest players are forcefully separated from each other without inflection as to who might be who. The best suggestion I can come up with is that supported distinction between players' special interests would better facilitate interaction and community of these interests.
I would suggest that as a specific character option, there is a drop down selection box of what interest the player's character has. In this case, the options would be "None", "PvP", and "Roleplay". Obviously, selecting "None" would have no effect on the current chat system and would carry on as normal. However, if a player selects "PvP" or "Roleplay", I can suggest one of the two following options.
a) Character names ( name @handle) of people with the same special interest selection as you are highlighted by a global color whenever they speak in any chat context, to include tells, private channels, zone, and/or emotes. This distinguishes players of your chosen special interest in chat so that players can pursue common interest activities with that identification in place.
b) Character names ( name @handle) of people with either "PvP" or "Roleplay" selected are highlighted by different global colors, say Orange for "PvP" and Cyan for "Roleplay".
What this would do is add distinction between players, and encourage them to develop as communities, knowing there are indeed fellow players with similar interests obviously apparent at a glance. Plus, it gives players a better idea at glance what to expect out of other players according to character chat color. Additionally, as some players like/want to do both PvP and Roleplay on different characters, they don't have to worry about changing color schemes every time they switch toons since the chat option is character based.
I could probably thing of a few more smaller, nagging, chat issues, but I think these three points are about as good a compromise of both what can be made available in STO, and what people have to to expect in MMO socializing. Feel free to discuss of make better suggestions.