It's important to note that the majority of Mat's memories are not his own, more random ones that the Aelfinn used to fill up the holes:
From a 2002 interview:
QUESTION Are all of Mat’s memories from his past lives?
ROBERT JORDAN No, Mat’s “old” memories are not from his past lives at
all. The “sickness” he got from the Shadar Logoth dagger resulted in
holes in his memory. He found whole stretches of his life that seemed
to be missing. When he passed through the “doorframe” ter’angreal in
Rhuidean, one of the things he said – not knowing that the rules here
were different than in the other ter’angreal he had used – was that he
wanted the holes in his memory filled up, meaning that he wanted to
recover his own memories. In this place, however, it was not a matter
of asking questions and receiving answers, but of striking bargains
for what you want. What he received for that particular demand was
memories gathered by the people on that side of the ter’angreal,
memories from many men, all long dead, from many cultures. And since
not everyone passing by has the nerve to journey through a ter’angreal
to some other world, the memories he received were those of
adventurers and soldiers and men of daring.
The question of the his early use of the old tongue seems to be a case of "the old blood":
LEE DAVIS The speaking the Old Tongue is from his bloodline though, not his memories in that case, isn't it?
BRANDON SANDERSON Yes, but it's still foreshadowing. He's the one who does it, not the others.
SLEEPINGHOUR In The Eye of the World, is Mat remembering the Old Tongue from his own past life or from his ancestors?
TEREZ Good question. He seems to have confirmed Old Blood for the Old Tongue, but the Aemon memory?
FELIX PAX That's what my belief is, Aemon. Mat Cauthon is the reborn soul of Aemon. Aemon's Old Tongue.
BRANDON SANDERSON It isn't made clear. It could be either. The implication is his bloodline
Is Rand's possible interaction with his past life special?
QUESTION Is one of the effects of the taint to lower the boundaries
between past lives or is Rand a special case?
Which brings us back to the nature of the voice in Rand's head.
In the Wheel of Time, one soul can have many personalities, regarding the Dark One, he's been shown to be able to capture a soul at time of death, with its current personality and place it in another body cleansing it of any issues e.g. Elan's insanity. There isn't any instances of the Dark One interacting with a soul's previous personalities.