Can rechargeable batteries with different mA values be used in the same device with good/normal results?
The simplest answer is that the camera will perform as if you used 2 1400mAh cells.

First, we'll start with the h (hours).  The mAh rating suggests the cell can produce that much current for an hour.  Being a Marketing number, you can read this as, "Will never perform better than...".  In real life, you can get near this performance at lower currents, but at high currents the run time diminishes significantly.

Assuming the two cells are operated in series, the current through them must be the same (basic electronic principle).  If we assume the numbers are accurate, and that the camera consumes 1.4A (it doesn't), then the 1400 cell goes dead in an hour, while the 2300 could have gone (2300/1400)*1hr= 1.6 hours, only, everything stops around the time the first cell goes dead.

When the cells go dead, the camera should shut off, but since the second cell is still going strong, it may run for a little extra time.  During that time, the smaller cell will continue to be discharged (the larger cell is now doing all the work). That first cell may go all the way to zero volts, and the start charging backwards.  This is where your "adverse issues" occur.

In Primary cells (the non-rechargeable ones) in particular, the normal chemical reactions eat away at the case, but since you take the cell out before it's completely dead, the integrity is maintained.  Discharge it fully, though, and the cell beings to leak, damaging your equipment. If you take it  out immediately, you'll be ok, but leave it in there and you risk damage.  

For rechargeable cells, running them down to nothing (or reversing them) will ruin them, and they may not recharge or run very long after that.  Here the damage is mostly financial (although rechargeable cells can leak as well).