Now using the web gui to sort smart matches as the FTB gui is unusable, I've managed to get these strange behaviors.
Image 1 (hits)The names are different, the years are different, still there seem to be a match, but when I open the compare trees function, I get image 2 (compared trees). Where it shows the same person. I can understand it being a match in the second case, but it's the same match, but in 2 different views.
I went over all of the rejected Smart Matches in your site for the person in the screenshot, and looked at the tree comparisons for them, and I was unable to reproduce what you are describing on my computer. Do you still see this in your site?
Here both Anne Nielsdatter on match 7 and 8 is the same person, why do they appear twice?: http://www.myheritage.no/FP/tree-matches.php?s=128288961&familyTreeID=1&targetFamilyTreeID=4&targetSiteID=143735511&reviewMode=pending
Here what's the match here between these brothers on match 49, Hans and Peder Pettersen Hønnichen: http://www.myheritage.no/FP/tree-matches.php?s=128288961&familyTreeID=1&targetFamilyTreeID=1&targetSiteID=150970871&reviewMode=pending
Here match 19Sophie Iversdatter / Marit Iversdatter Myklebostad where Marit is changing to Sophie when entering tree comparison: http://www.myheritage.no/FP/tree-matches.php?s=128288961&familyTreeID=1&targetFamilyTreeID=4&targetSiteID=147630671&reviewMode=pending
Just checked this particular person and it's okay now. Haven't seen this fault in a while. This time the match was Hans and Nils. The tree comparison showd both Nils. Then after I'd rejected the person, it showd Nils and Jens in the comparison tree. I might have remembered the names incorrectly, but you'll get the idea.
It seems that when I use tree comparison it goes into another tree. The persons are completely different. Or missing dates are suddenly not missed anymore. Had I only known which was the correct view.
I don't do the same you do. I'm using the "ventende bekreftelser" (waiting confirmation) to see who matches and who don't. And when I see someone I'm unsure about I click the "sammenligne traer" (compare trees) from the individual drop down list on the right. This takes me to the tree comparison, but it's here the name changes to match the smart match percent. So it seems SM is using the tree comparison name, but sometimes showing a different name in the waiting confirmations screen.
For some reason this web page did not approve of the word "select" in my post above so I changed it to click; strange thing.
Looks like this problem is caused by some corruption in our smart matches pools. Sometimes individuals get a match with another person, and also with this person's sibling (as in the case you mentioned). The transitive nature of this link of matches can cause havoc in our system.
This requires a deep infrastructural change to the Smart Matches mechanism, which we will be able to make in the next version of this feature.
I am not sure when this will happen, but I will notify you when changes are made.