Right - I’m not saying “don’t make uncertainty rise”.
For sure that should still happen.
I’m just saying I’m not yet seeing the relevance of it.
The problem with the 13k starting rank is not just “the person has high uncertainty”. The problem is “they are out of their league”.
If we explore going away for a while: suppose you played steadily and become 13k +/- 2 (lets say). Then you went away for a while so your uncertainty rose and you you became 13k ± 6 (lets say).
Now … have you really forgotten everything? It seems very unlikely. A 13k who hasn’t played for 5 years will still know corner centre sides and basic shape. So they are at least 19k. So they can use the rank pairing settings in the get-a-game system to get a match with someone at that level. It’s not like they are 25k and compltely out of their league witih a wrong rating.
Now that I’ve typed this, I can see my suggestion of using the previous rank as a qualifying rank is incorrect.
In fact, if you hav been away so long that your established rank is totally wrong, then you should just start a new account, and select a new qualifying rank. 
Like this person did.
(And isn’t it fascinating that in that thread we had to point out to them that they would not immediately get the effect they wanted from doing this: they wanted to stop being paired with people 15-16k, because they were no longer that good. But ironically in the current system making a new account makes this problem worse!)
GaJ