As much as it would be nice to claim bipolar people are smarter than the norm - statistics say there is an equal mix. Bipolar does not disciminate. I have met a few 'stupid' bipolar people! lol. And some scary intelligent ones too. They have shown a higher number of bipolar people in the arts though so there may be a link to creativity. Kay Jameson has a book "Touched by Fire" about this.
As for word salad. I find I am doing that too. I think the culprit may be meds. Garage - garbage, they - thy, it - is, rein, reign that sort thing. I have to be careful and reread text before I send it out.
As Amy4891 asked, are there racing thoughts? I myself will start to stutter badly when I'm manic or upset. The brain is just producing thoughts and words faster than my mouth can articulate. This illness affects people in so many different ways... Again, I wouldn't freak out too much. In my opinion, focus on the illness and not the symptoms. You might also consider talking to your health provider about being back on meds...
Are you having any racing thoughts? I had touble with this in the second half of my manic phase. For me I think it was like my brain was shorting out from too much activity. Inability to go as fast as my mind was. I wouldn't freak on it too much though....language is so obscure anyways....