I can't be the only one who finds this obnoxious. Every time you do several STFs or other team events consecutively, these little indicators ('fleet,' 'team,' 'fleet,' 'team...') switch between each other when you enter and exit the teams you join. This takes up space on the chat UI element, but doesn't actually move or expand it, which in turn causes the chat display window to be squished into oblivion. The image linked is only a mild example; with a little more time spent playing, the chat window would have become completely unusable.
So far I've found no way of preventing this, and the only way I've found of correcting it is to log off and on again.