Technically structural type alloys should be heat treated to give them strength, any heat from welding can cause this area to weaken, so a welded rim will be slightly weaker in this area, but it will still be stronger than a cracked rim. The anodizing may have made the weld more brittle perhaps?? did you run this problem past the anodizers?
I have welded a few rims but have always considered it a budget repair, if you are going to the trouble of relacing a wheel I would be more inclined to source a good rim. Unless it was some type of rare rim.
If the crack is 'Veed" out before welding then their is no reason why it can't be ground back smooth, but leaving the weld their will retain a bit more strength. I have always ground welds back on rims & comebacks are rare.
This sort of thing can never be guaranteed because their are so many variables such as spoke tightness, 70 foot triples etc.
Welding should be fine but simply keep an eye on it from time to time.