Hi DesuDeus, if the "triangles" are actually made up of trimmed planes, you could try doing a separate on them and then select them both and do boolean union.

There is a mechanism built into boolean union that tries to simplify coplanar fragments into larger single big trimmed planes and removes the edges between them.

That will not work if the triangles are formed with a pole (one surface side collapsed down to a single point) rather than a trimmed plane though. If you separate out one triangle and then look at its surface control points, is the triangle a trimmed out area of a larger plane surface or do you only see 3 control points for the entire surface?

- Michael