Is it legal for someone with a Pensionado Visa to cross the border for 90 days to keep from becoming a tax resident.
Yes.
, or would it affect their chances for getting it renewed?
No (providing you stay at least 183 days in Argentina).
You need to be in Argentina for a minimum of 183 days in the first 12 months to be able to renew your temporary residency into a second period of 12 months. And so on, every year.
If you leave Argentina for 90 days during the 12 months (i.e., spend between 183 and, say, 273 days in Argentina during the 365 days), you do not become a tax resident at the end of the 12 months. You would need to continue this pattern every 12 months in order to avoid becoming a tax resident.
Further to the other threat, where you have raised this same issue, according to the following article the minimum threshold for paying
ganancias tax in March was monthly income of 2,280,647 pesos:
La agencia recaudadora ajustó las escalas en función de la evolución del Índice de Precios al Consumidor, según lo que marca la ley de reforma fiscal. Hasta cuándo se puede presentar la declaración jurada y realizar el pago.
www.cronista.com
At the March exchange rate, the equivalent in US$ was around $2,140. So, if your monthly pension amounts to less than that total (the precise amount will fluctuate over time, depending on various factors, but you get the idea of the scale), it doesn't matter that you may have become, technically, a tax resident of Argentina--you are below the tax threshold and do not have to pay.