200ms seems to iteract badly with some digital systems, causing
unreliable blinking.

I will turn the cycle interval into a configuration variable in 8.0.

200ms = original value, unreliable blinking
500ms = acceptable blinking with walksnail
1000ms = was also tested and worked ok

For software blink emulation, Blinking changes a character appearance
at a given frequency, the OSD code on digital systems updates the OSD at a
different arbitrary frequency. Depending on the relationship between the two
you may not see the text, or it may not blink. Similar to how lights can
blink if you have mismatched frequencies when recording video (50Hz
mains, 60fps video).

I also suspect that the way some of the digital systems handle blinking characters
may rely on the clear screen command, which also happens at a given
frequency in INAV.

Looks like display.c already handles it,
and displayport_msp is always using sw blinking.