Right angle traces

[AlfBaz]

So for length matching, would this be a definite no-no?

That would be a no-no, but not for signal integrity reasons. It's a no-no for manufacturability. Especially when using small geometries. If the amplitude vs repetition distance ratio is large then you will get etching problems ( amplitude is how tall the matching weave is compared to the opening between the tracks and width of track.) For a dense weave you need either chamfered or rounded turns.

Signal integrity is not affected. It is purely a processing problem. The sharp corners are prone to resist peeling when they scrub the boards . After developing the boards are scrubbed with brushes. Sharp outside edges can get damaged. Either lifting the resist or ripping it off.
During etch the outward facing corner gets attacked from both sides. This gives an underetch
If the resist was te lift during etch (we are spray etching under high pressure these days) this can give thickness variations and all kind of other problems that will cause the board to be rejected during inspection. The trace is not necessarily et hed open, it is irregular , the corner is slanted and visual inspection will fail this board as a reject. This cost money for the board fab.

So they dont like this.

Again, if you are doing 8 mil traces it is ok , but start messing around at 4 mil and below and the board house will contact you and request bot to do this, or they will increase the price as the yield goes down.

Thanks for the insight FE
 

[AlfBaz]

Would the sharp edge of a corner be a slightly better antenna thereby promoting coupling to adjacent parallel tracks like those in a multilane bus?

Ran some quick simulations
4/4mil track space 2ns rise times, same layer stackup, 2 tracks on top layer

The drive ends of the tracks start far away in one instance the approach is 45 deg the other 90, run together for about 0.4" and then seperate

The 45 degree approach, with a longer parallel run required 240mV threshold setting to avoid coupling indication
90 degree approach, with a shorter parallel run required 450mV threshold setting to avoid coupling

[AlfBaz]

EMI simulation also revealed higher emissions with the right angles

for the pics below
RA = Right angles
NRA = No right angles

Edit: in the pics below, ignore the lines at the top, they're different emission limits for various standards