I apologise in advance if this is too obvious/basic for almost all players, but after seeing quite a few mouse slips in TL games I thought posting here wouldn't be such a terrible idea. If one single player can benefit from this, it's more than worth it for me.

From my experience mouse slips are essentially related to the need to hold the button while moving the mouse, so changing from drag-and-drop to click-and-click has made it a forgotten issue for me. In BabasChess, go to Preferences > Board > Piece Movement, where you can see a board named Move input. The default option is 'Drag pieces', but by unchecking that box you'll just click on a piece and the target square to move it. No need to hold the mouse button while moving it.

I invite users of other FICS clients to inform people of a similar feature in such programs.

Wishing everybody a good and mouse slip-free 2018,
Roberto (Beto).

That is major improvement.

Other way to skip mouseslips is to write the moves on console.

As an interesting aside I've had a player in my team that has done what could be called a console slip when they typed Re6 instead of Re3 and losing a rook and the game.

Personally I find that way to prevent mouse slips is to make sure you have a decent mouse as most mouse slips are due to failures in mouse itself (i.e. button unreliable or movement is dodgy). Secondly I always aim for middle of square that way I have an error margin for a slight movement of wrist upon release of mouse button.

Of course in some scenarios a decent mouse isn't an option. If using a touchscreen interface then kurumin's suggestion would work a lot better and same applies if you have an old mouse or one with reliability issues