Acute angle on a pad or a via
These are fine. There are no acute angles in the examples you've given. In the first one, the angles are 135° and 90°. In the second one, the traces are on different layers. The reason that you are often advised not to use acute angles is that they may trap etching solution, so you may end up with over etching in the elbows. This may be a problem on very narrow, or impedance controlled, traces but shouldn't cause major problems on larger traces.

To expand a little, aside from the over etching issue, there are two signal integrity reasons you may need to consider with right or acute angles. Firstly, there's high speed signals (e.g. clock or RF) where the tighter turn may cause reflections. Secondly, sharp turns may cause current crowding in very high current traces, which increases the probability of overheating and failure at the turn.