For BS players, never split Tens.
For card counters: Assuming Hi-Lo for multi-deck, it's TC 4, 5, and 6 for a dealer upcard of 6, 5, and 4, respectively. Split tens in these situations if you don't like giving up lots of EV just because you heard that it was a bad move. Especially if you're playing unrated, with short sessions, in a place that you don't play at all the time. If you're a regular, it'll be a lot harder to pull off and probably worth less when considering longevity, but you shouldn't rule the play out entirely.
I would also recommend not avoiding correct use of the surrender option (including indices) or the insurance option, even though those both also bring comments from players and dealers and scrutiny from the pit (especially insurance).