Hi Dave!
About the sprite design we had that debate with Errazking, the graphic designer. We did some tests and we decided that aesthetically they looked better without the black border. As the sprite was in multicolour mode, the border was too wide and saturated the design with black. An overlay with a high-resolution sprite as a border was also not viable because multiplexing was not possible. It has to be taken into account that there are situations where all 8 sprites can be on the same platform height. In any case I'm glad to hear that it didn't cause any major problems.
As for the sentry overlapping is a ‘defect’ already detected and discussed in randoom 1. There are fairly simple ways to mitigate or even fix it, but we decided that it is an addition to the difficulty of the game that adds the incentive to be attentive to the remaining colours to avoid falling into the trap of hunting a sentry ‘escorted’.
On the ‘continue’ part, you are absolutely right. I'll make a list of issues to fix to update the version soon.
Thank you very much for your feedback!