Insufficient material to mate.

The old ruleset leads to situation where your opponent can sit down his clock in positions where you have a forced mate.

@kenzaburo the issue is that it is frequent, due to the number of games being played. It may be "rare" i.e. once every 5000 games but if there are 100 000 games played every day, then it's a "common" problem, especially if each game ends up on the forum.

I made those numbers up btw, I have no idea what the actual situation is.

Also, don't know if this has been said on this post yet but: if you don't want the possibility of pointless click races, play with increment. Also, as @lovlas points out, the situation used to be much worse: I remember a forum post where one side had K+N and the other side had a load of (in)conveniently arranged pieces. Side with K+N had mate in 1. Opponent knew this so let their time run down: result was a draw. Games like that were why the rule was changed to what it is now AFAIK.

@lovlas That's something that 'might' have happened every once in a blue moon. The lichess rule is something that distorts endgames thousands of times per day, each and every day. If that was the genuine reason for the rule then it's one of the best examples I've ever seen of cutting off the nose to spite the face.

Lichess has a number of annoying idiosyncratic rules or functions, although the one discussed by the OP is not one of them. In a thread several weeks ago I complained about premoving, which upsets standard blitz strategy. I do not agree that any rule is justified that enhances experience in some general way. We are here to play chess, not chess plus some new rules that enhance experience. Mutatis mutandis - given that online experience naturally has some differences with the physical moving of pieces OTB - an online site should mirror the real game (OTB) as much as possible - especially by preserving te framework for the same strategies - unless one selects a variant.

Yes, rules do change. I think the Spanish introduced the two square opening pawn option around the 16th century to speed up the opening. Thank them for that. The 50 rule limit was introduced by FIDE a few decades ago, and modified a few times. But today only FIDE should have the authority to make any changes, and it ought to be ultra-conservative in exercising that authority, out of respect for a venerable game played and studied all over the world by many millions of people, and embedded in our languages and cultures. So far as I know, FIDE does exercise that authority conservatively, and sites should follow along by reflecting FIDE rules. With respect to the rule in question here, if mate is possible FIDE is right to allow a loss on time, and Lichess in turn for following FIDE.

@mCoombes314 Say 1 in 10k. Half of the times I'll be faster, half of the times you'll flag me. Doesn't seem to affect balance so much. If you flag me more often probably you're higher rated (you got there with more time) so it doesn't really seem to reflect on anything. Just tries to be rule accurate.

And personally I'm all for the pointless click races, this way chess comes closer to melee.

-snipped- Misread @mCoombes314 K+B as N+B somehow.

Can anyone explain the word „insufficient“? How many exceptions is „insufficient“?

Funny. This little thing comes up so often. Literally just had it occur in a game: lichess.org/scqu4t0i/black#111

4 pawns versus a single bishop. I think in a million games this will never feel correct to adjudicate games like that a loss (had the 4 pawns flagged).

What about 8 queens vs a lone pawn?

Check it out, USCF released part of their rulebook, with new ILC rules! Good luck translating these into algorithms:
http://www.uschess.org/content/view/7752/369/

The TD should be aware that common practice has shown that in addition to the official Blitz rules that “Insufficient Losing Chances” claims are upheld only:
1.) If both players each have just one identical piece and if neither side can show a forced win.
2.) In K+bishop vs. K+bishop of opposite colors, with only 1 pawn on the board, provided there is no forced win.
3.) K+rook pawn vs. K can be claimed as a draw once the defender is on the rook file in front of the pawn. K+pawn vs. K can be claimed as a draw once the defender is immediately on the square directly in front of the pawn as long as it’s not on the 7th rank.
4.) K+rook+rook pawn vs. K+rook is a draw if the pawn is blockaded by the king and there is no immediate win.
5.) The claimant has a significant material and positional advantage.